diff --git a/include/weave/error.h b/include/weave/error.h
index 64b99bd..0cf8dc5 100644
--- a/include/weave/error.h
+++ b/include/weave/error.h
@@ -24,6 +24,21 @@
  public:
   ~Error() = default;
 
+  class AddToTypeProxy {
+   public:
+    operator bool() const { return false; }
+
+    template <class T>
+    operator std::unique_ptr<T>() const {
+      return nullptr;
+    }
+
+    template <class T>
+    operator T*() const {
+      return nullptr;
+    }
+  };
+
   // Creates an instance of Error class.
   static ErrorPtr Create(const tracked_objects::Location& location,
                          const std::string& code,
@@ -35,17 +50,17 @@
   // If |error| is not nullptr, creates another instance of Error class,
   // initializes it with specified arguments and adds it to the head of
   // the error chain pointed to by |error|.
-  static void AddTo(ErrorPtr* error,
-                    const tracked_objects::Location& location,
-                    const std::string& code,
-                    const std::string& message);
+  static AddToTypeProxy AddTo(ErrorPtr* error,
+                              const tracked_objects::Location& location,
+                              const std::string& code,
+                              const std::string& message);
   // Same as the Error::AddTo above, but allows to pass in a printf-like
   // format string and optional parameters to format the error message.
-  static void AddToPrintf(ErrorPtr* error,
-                          const tracked_objects::Location& location,
-                          const std::string& code,
-                          const char* format,
-                          ...) PRINTF_FORMAT(4, 5);
+  static AddToTypeProxy AddToPrintf(ErrorPtr* error,
+                                    const tracked_objects::Location& location,
+                                    const std::string& code,
+                                    const char* format,
+                                    ...) PRINTF_FORMAT(4, 5);
 
   // Clones error with all inner errors.
   ErrorPtr Clone() const;
diff --git a/src/commands/command_instance.cc b/src/commands/command_instance.cc
index dba14c4..fc9b0e7 100644
--- a/src/commands/command_instance.cc
+++ b/src/commands/command_instance.cc
@@ -37,10 +37,10 @@
 bool ReportInvalidStateTransition(ErrorPtr* error,
                                   Command::State from,
                                   Command::State to) {
-  Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidState,
-                     "State switch impossible: '%s' -> '%s'",
-                     EnumToString(from).c_str(), EnumToString(to).c_str());
-  return false;
+  return Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidState,
+                            "State switch impossible: '%s' -> '%s'",
+                            EnumToString(from).c_str(),
+                            EnumToString(to).c_str());
 }
 
 }  // namespace
@@ -152,10 +152,9 @@
     // Make sure the "parameters" property is actually an object.
     const base::DictionaryValue* params_dict = nullptr;
     if (!params_value->GetAsDictionary(&params_dict)) {
-      Error::AddToPrintf(error, FROM_HERE, errors::json::kObjectExpected,
-                         "Property '%s' must be a JSON object",
-                         commands::attributes::kCommand_Parameters);
-      return params;
+      return Error::AddToPrintf(error, FROM_HERE, errors::json::kObjectExpected,
+                                "Property '%s' must be a JSON object",
+                                commands::attributes::kCommand_Parameters);
     }
     params.reset(params_dict->DeepCopy());
   } else {
@@ -180,10 +179,9 @@
   // Get the command JSON object from the value.
   const base::DictionaryValue* json = nullptr;
   if (!value->GetAsDictionary(&json)) {
-    Error::AddTo(error, FROM_HERE, errors::json::kObjectExpected,
-                 "Command instance is not a JSON object");
     command_id->clear();
-    return instance;
+    return Error::AddTo(error, FROM_HERE, errors::json::kObjectExpected,
+                        "Command instance is not a JSON object");
   }
 
   // Get the command ID from 'id' property.
@@ -193,16 +191,15 @@
   // Get the command name from 'name' property.
   std::string command_name;
   if (!json->GetString(commands::attributes::kCommand_Name, &command_name)) {
-    Error::AddTo(error, FROM_HERE, errors::commands::kPropertyMissing,
-                 "Command name is missing");
-    return instance;
+    return Error::AddTo(error, FROM_HERE, errors::commands::kPropertyMissing,
+                        "Command name is missing");
   }
 
   auto parameters = GetCommandParameters(json, error);
   if (!parameters) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kCommandFailed,
-                       "Failed to validate command '%s'", command_name.c_str());
-    return instance;
+    return Error::AddToPrintf(
+        error, FROM_HERE, errors::commands::kCommandFailed,
+        "Failed to validate command '%s'", command_name.c_str());
   }
 
   instance.reset(new CommandInstance{command_name, origin, *parameters});
diff --git a/src/component_manager_impl.cc b/src/component_manager_impl.cc
index a4f5740..550775d 100644
--- a/src/component_manager_impl.cc
+++ b/src/component_manager_impl.cc
@@ -47,18 +47,17 @@
       return false;
   }
   if (root->GetWithoutPathExpansion(name, nullptr)) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidState,
-                       "Component '%s' already exists at path '%s'",
-                       name.c_str(), path.c_str());
-    return false;
+    return Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidState,
+                              "Component '%s' already exists at path '%s'",
+                              name.c_str(), path.c_str());
   }
 
   // Check to make sure the declared traits are already defined.
   for (const std::string& trait : traits) {
     if (!FindTraitDefinition(trait)) {
-      Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidPropValue,
-                         "Trait '%s' is undefined", trait.c_str());
-      return false;
+      return Error::AddToPrintf(error, FROM_HERE,
+                                errors::commands::kInvalidPropValue,
+                                "Trait '%s' is undefined", trait.c_str());
     }
   }
   std::unique_ptr<base::DictionaryValue> dict{new base::DictionaryValue};
@@ -108,10 +107,9 @@
   }
 
   if (!root->RemoveWithoutPathExpansion(name, nullptr)) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidState,
-                       "Component '%s' does not exist at path '%s'",
-                       name.c_str(), path.c_str());
-    return false;
+    return Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidState,
+                              "Component '%s' does not exist at path '%s'",
+                              name.c_str(), path.c_str());
   }
 
   for (const auto& cb : on_componet_tree_changed_)
@@ -132,18 +130,17 @@
 
   base::ListValue* array_value = nullptr;
   if (!root->GetListWithoutPathExpansion(name, &array_value)) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidState,
-                       "There is no component array named '%s' at path '%s'",
-                       name.c_str(), path.c_str());
-    return false;
+    return Error::AddToPrintf(
+        error, FROM_HERE, errors::commands::kInvalidState,
+        "There is no component array named '%s' at path '%s'", name.c_str(),
+        path.c_str());
   }
 
   if (!array_value->Remove(index, nullptr)) {
-    Error::AddToPrintf(
+    return Error::AddToPrintf(
         error, FROM_HERE, errors::commands::kInvalidState,
         "Component array '%s' at path '%s' does not have an element %zu",
         name.c_str(), path.c_str(), index);
-    return false;
   }
 
   for (const auto& cb : on_componet_tree_changed_)
@@ -233,11 +230,10 @@
     return nullptr;
 
   if (role < minimal_role) {
-    Error::AddToPrintf(error, FROM_HERE, "access_denied",
-                       "User role '%s' less than minimal: '%s'",
-                       EnumToString(role).c_str(),
-                       EnumToString(minimal_role).c_str());
-    return nullptr;
+    return Error::AddToPrintf(error, FROM_HERE, "access_denied",
+                              "User role '%s' less than minimal: '%s'",
+                              EnumToString(role).c_str(),
+                              EnumToString(minimal_role).c_str());
   }
 
   std::string component_path = command_instance->GetComponent();
@@ -248,12 +244,11 @@
         SplitAtFirst(command_instance->GetName(), ".", true).first;
     component_path = FindComponentWithTrait(trait_name);
     if (component_path.empty()) {
-      Error::AddToPrintf(
+      return Error::AddToPrintf(
           error, FROM_HERE, "unrouted_command",
           "Unable route command '%s' because there is no component supporting"
           "trait '%s'",
           command_instance->GetName().c_str(), trait_name.c_str());
-      return nullptr;
     }
     command_instance->SetComponent(component_path);
   }
@@ -279,10 +274,9 @@
   }
 
   if (!trait_supported) {
-    Error::AddToPrintf(error, FROM_HERE, "trait_not_supported",
-                       "Component '%s' doesn't support trait '%s'",
-                       component_path.c_str(), pair.first.c_str());
-    return nullptr;
+    return Error::AddToPrintf(error, FROM_HERE, "trait_not_supported",
+                              "Component '%s' doesn't support trait '%s'",
+                              component_path.c_str(), pair.first.c_str());
   }
 
   if (command_id.empty()) {
@@ -353,10 +347,9 @@
                                           ErrorPtr* error) const {
   const base::DictionaryValue* command = FindCommandDefinition(command_name);
   if (!command) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidCommandName,
-                       "Command definition for '%s' not found",
-                       command_name.c_str());
-    return false;
+    return Error::AddToPrintf(
+        error, FROM_HERE, errors::commands::kInvalidCommandName,
+        "Command definition for '%s' not found", command_name.c_str());
   }
   std::string value;
   // The JSON definition has been pre-validated already in LoadCommands, so
@@ -414,22 +407,22 @@
     return nullptr;
   auto pair = SplitAtFirst(name, ".", true);
   if (pair.first.empty()) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kPropertyMissing,
-                       "Empty state package in '%s'", name.c_str());
-    return nullptr;
+    return Error::AddToPrintf(error, FROM_HERE,
+                              errors::commands::kPropertyMissing,
+                              "Empty state package in '%s'", name.c_str());
   }
   if (pair.second.empty()) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kPropertyMissing,
-                       "State property name not specified in '%s'",
-                       name.c_str());
-    return nullptr;
+    return Error::AddToPrintf(
+        error, FROM_HERE, errors::commands::kPropertyMissing,
+        "State property name not specified in '%s'", name.c_str());
   }
   std::string key = base::StringPrintf("state.%s", name.c_str());
   const base::Value* value = nullptr;
   if (!component->Get(key, &value)) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kPropertyMissing,
-                       "State property '%s' not found in component '%s'",
-                       name.c_str(), component_path.c_str());
+    return Error::AddToPrintf(error, FROM_HERE,
+                              errors::commands::kPropertyMissing,
+                              "State property '%s' not found in component '%s'",
+                              name.c_str(), component_path.c_str());
   }
   return value;
 }
@@ -441,15 +434,14 @@
   base::DictionaryValue dict;
   auto pair = SplitAtFirst(name, ".", true);
   if (pair.first.empty()) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kPropertyMissing,
-                       "Empty state package in '%s'", name.c_str());
-    return false;
+    return Error::AddToPrintf(error, FROM_HERE,
+                              errors::commands::kPropertyMissing,
+                              "Empty state package in '%s'", name.c_str());
   }
   if (pair.second.empty()) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kPropertyMissing,
-                       "State property name not specified in '%s'",
-                       name.c_str());
-    return false;
+    return Error::AddToPrintf(
+        error, FROM_HERE, errors::commands::kPropertyMissing,
+        "State property name not specified in '%s'", name.c_str());
   }
   dict.Set(name, value.DeepCopy());
   return SetStateProperties(component_path, dict, error);
@@ -673,26 +665,24 @@
     auto element = SplitAtFirst(parts[i], "[", true);
     int array_index = -1;
     if (element.first.empty()) {
-      Error::AddToPrintf(error, FROM_HERE, errors::commands::kPropertyMissing,
-                         "Empty path element at '%s'", root_path.c_str());
-      return nullptr;
+      return Error::AddToPrintf(
+          error, FROM_HERE, errors::commands::kPropertyMissing,
+          "Empty path element at '%s'", root_path.c_str());
     }
     if (!element.second.empty()) {
       if (element.second.back() != ']') {
-        Error::AddToPrintf(error, FROM_HERE, errors::commands::kPropertyMissing,
-                           "Invalid array element syntax '%s'",
-                           parts[i].c_str());
-        return nullptr;
+        return Error::AddToPrintf(
+            error, FROM_HERE, errors::commands::kPropertyMissing,
+            "Invalid array element syntax '%s'", parts[i].c_str());
       }
       element.second.pop_back();
       std::string index_str;
       base::TrimWhitespaceASCII(element.second, base::TrimPositions::TRIM_ALL,
                                 &index_str);
       if (!base::StringToInt(index_str, &array_index) || array_index < 0) {
-        Error::AddToPrintf(error, FROM_HERE,
-                           errors::commands::kInvalidPropValue,
-                           "Invalid array index '%s'", element.second.c_str());
-        return nullptr;
+        return Error::AddToPrintf(
+            error, FROM_HERE, errors::commands::kInvalidPropValue,
+            "Invalid array index '%s'", element.second.c_str());
       }
     }
 
@@ -701,10 +691,10 @@
       // points to the actual parent component. We need the root to point to
       // the 'components' element containing child sub-components instead.
       if (!root->GetDictionary("components", &root)) {
-        Error::AddToPrintf(error, FROM_HERE, errors::commands::kPropertyMissing,
-                           "Component '%s' does not exist at '%s'",
-                           element.first.c_str(), root_path.c_str());
-        return nullptr;
+        return Error::AddToPrintf(error, FROM_HERE,
+                                  errors::commands::kPropertyMissing,
+                                  "Component '%s' does not exist at '%s'",
+                                  element.first.c_str(), root_path.c_str());
       }
     }
 
@@ -717,16 +707,16 @@
     }
 
     if (value->GetType() == base::Value::TYPE_LIST && array_index < 0) {
-      Error::AddToPrintf(error, FROM_HERE, errors::commands::kTypeMismatch,
-                         "Element '%s.%s' is an array", root_path.c_str(),
-                         element.first.c_str());
-      return nullptr;
+      return Error::AddToPrintf(error, FROM_HERE,
+                                errors::commands::kTypeMismatch,
+                                "Element '%s.%s' is an array",
+                                root_path.c_str(), element.first.c_str());
     }
     if (value->GetType() == base::Value::TYPE_DICTIONARY && array_index >= 0) {
-      Error::AddToPrintf(error, FROM_HERE, errors::commands::kTypeMismatch,
-                         "Element '%s.%s' is not an array", root_path.c_str(),
-                         element.first.c_str());
-      return nullptr;
+      return Error::AddToPrintf(error, FROM_HERE,
+                                errors::commands::kTypeMismatch,
+                                "Element '%s.%s' is not an array",
+                                root_path.c_str(), element.first.c_str());
     }
 
     if (value->GetType() == base::Value::TYPE_DICTIONARY) {
@@ -737,11 +727,10 @@
       const base::Value* component_value = nullptr;
       if (!component_array->Get(array_index, &component_value) ||
           !component_value->GetAsDictionary(&root)) {
-        Error::AddToPrintf(error, FROM_HERE, errors::commands::kPropertyMissing,
-                           "Element '%s.%s' does not contain item #%d",
-                           root_path.c_str(), element.first.c_str(),
-                           array_index);
-        return nullptr;
+        return Error::AddToPrintf(
+            error, FROM_HERE, errors::commands::kPropertyMissing,
+            "Element '%s.%s' does not contain item #%d", root_path.c_str(),
+            element.first.c_str(), array_index);
       }
     }
     if (!root_path.empty())
diff --git a/src/device_registration_info.cc b/src/device_registration_info.cc
index 0c4a5d7..7c20084 100644
--- a/src/device_registration_info.cc
+++ b/src/device_registration_info.cc
@@ -196,10 +196,9 @@
       SplitAtFirst(response.GetContentType(), ";", true).first;
 
   if (content_type != http::kJson && content_type != http::kPlain) {
-    Error::AddTo(
+    return Error::AddTo(
         error, FROM_HERE, "non_json_content_type",
         "Unexpected content type: \'" + response.GetContentType() + "\'");
-    return std::unique_ptr<base::DictionaryValue>();
   }
 
   const std::string& json = response.GetData();
@@ -328,10 +327,11 @@
 
   VLOG(2) << "Device registration record "
           << ((have_credentials) ? "found" : "not found.");
-  if (!have_credentials)
-    Error::AddTo(error, FROM_HERE, "device_not_registered",
-                 "No valid device registration record found");
-  return have_credentials;
+  if (!have_credentials) {
+    return Error::AddTo(error, FROM_HERE, "device_not_registered",
+                        "No valid device registration record found");
+  }
+  return true;
 }
 
 std::unique_ptr<base::DictionaryValue>
@@ -352,8 +352,7 @@
     if (!resp->GetString("error_description", &error_message)) {
       error_message = "Unexpected OAuth error";
     }
-    Error::AddTo(error, FROM_HERE, error_code, error_message);
-    return std::unique_ptr<base::DictionaryValue>();
+    return Error::AddTo(error, FROM_HERE, error_code, error_message);
   }
   return resp;
 }
@@ -836,9 +835,8 @@
     const std::string& service_url,
     ErrorPtr* error) {
   if (HaveRegistrationCredentials()) {
-    Error::AddTo(error, FROM_HERE, kErrorAlreayRegistered,
-                 "Unable to change config for registered device");
-    return false;
+    return Error::AddTo(error, FROM_HERE, kErrorAlreayRegistered,
+                        "Unable to change config for registered device");
   }
   Config::Transaction change{config_};
   change.set_client_id(client_id);
diff --git a/src/error.cc b/src/error.cc
index ced91e5..cb279c1 100644
--- a/src/error.cc
+++ b/src/error.cc
@@ -39,10 +39,10 @@
   return ErrorPtr(new Error(location, code, message, std::move(inner_error)));
 }
 
-void Error::AddTo(ErrorPtr* error,
-                  const tracked_objects::Location& location,
-                  const std::string& code,
-                  const std::string& message) {
+Error::AddToTypeProxy Error::AddTo(ErrorPtr* error,
+                                   const tracked_objects::Location& location,
+                                   const std::string& code,
+                                   const std::string& message) {
   if (error) {
     *error = Create(location, code, message, std::move(*error));
   } else {
@@ -50,18 +50,21 @@
     // we still want to log the error...
     LogError(location, code, message);
   }
+  return {};
 }
 
-void Error::AddToPrintf(ErrorPtr* error,
-                        const tracked_objects::Location& location,
-                        const std::string& code,
-                        const char* format,
-                        ...) {
+Error::AddToTypeProxy Error::AddToPrintf(
+    ErrorPtr* error,
+    const tracked_objects::Location& location,
+    const std::string& code,
+    const char* format,
+    ...) {
   va_list ap;
   va_start(ap, format);
   std::string message = base::StringPrintV(format, ap);
   va_end(ap);
   AddTo(error, location, code, message);
+  return {};
 }
 
 ErrorPtr Error::Clone() const {
diff --git a/src/privet/auth_manager.cc b/src/privet/auth_manager.cc
index 0753a2b..66d04c4 100644
--- a/src/privet/auth_manager.cc
+++ b/src/privet/auth_manager.cc
@@ -65,14 +65,13 @@
                      ErrorPtr* error) {
   UwMacaroonCaveatType caveat_type{};
   if (!uw_macaroon_caveat_get_type_(&caveat, &caveat_type)) {
-    Error::AddTo(error, FROM_HERE, kInvalidTokenError, "Unable to get type");
-    return false;
+    return Error::AddTo(error, FROM_HERE, kInvalidTokenError,
+                        "Unable to get type");
   }
 
   if (caveat_type != type) {
-    Error::AddTo(error, FROM_HERE, kInvalidTokenError,
-                 "Unexpected caveat type");
-    return false;
+    return Error::AddTo(error, FROM_HERE, kInvalidTokenError,
+                        "Unexpected caveat type");
   }
 
   return true;
@@ -86,8 +85,8 @@
     return false;
 
   if (!uw_macaroon_caveat_get_value_uint_(&caveat, value)) {
-    Error::AddTo(error, FROM_HERE, kInvalidTokenError, "Unable to read caveat");
-    return false;
+    return Error::AddTo(error, FROM_HERE, kInvalidTokenError,
+                        "Unable to read caveat");
   }
 
   return true;
@@ -103,8 +102,8 @@
   const uint8_t* start{nullptr};
   size_t size{0};
   if (!uw_macaroon_caveat_get_value_str_(&caveat, &start, &size)) {
-    Error::AddTo(error, FROM_HERE, kInvalidTokenError, "Unable to read caveat");
-    return false;
+    return Error::AddTo(error, FROM_HERE, kInvalidTokenError,
+                        "Unable to read caveat");
   }
 
   value->assign(reinterpret_cast<const char*>(start), size);
@@ -144,8 +143,8 @@
   buffer->resize(kMaxMacaroonSize);
   if (!uw_macaroon_load_(token.data(), token.size(), buffer->data(),
                          buffer->size(), macaroon)) {
-    Error::AddTo(error, FROM_HERE, kInvalidTokenError, "Invalid token format");
-    return false;
+    return Error::AddTo(error, FROM_HERE, kInvalidTokenError,
+                        "Invalid token format");
   }
   return true;
 }
@@ -155,9 +154,8 @@
                     ErrorPtr* error) {
   CHECK_EQ(kSha256OutputSize, secret.size());
   if (!uw_macaroon_verify_(&macaroon, secret.data(), secret.size())) {
-    Error::AddTo(error, FROM_HERE, "invalid_signature",
-                 "Invalid token signature");
-    return false;
+    return Error::AddTo(error, FROM_HERE, "invalid_signature",
+                        "Invalid token signature");
   }
   return true;
 }
@@ -271,23 +269,20 @@
                   &user_id, error) ||
       !ReadCaveat(macaroon.caveats[2], kUwMacaroonCaveatTypeExpiration,
                   &expiration, error)) {
-    Error::AddTo(error, FROM_HERE, errors::kInvalidAuthorization,
-                 "Invalid token");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kInvalidAuthorization,
+                        "Invalid token");
   }
 
   AuthScope auth_scope{FromMacaroonScope(scope)};
   if (auth_scope == AuthScope::kNone) {
-    Error::AddTo(error, FROM_HERE, errors::kInvalidAuthorization,
-                 "Invalid token data");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kInvalidAuthorization,
+                        "Invalid token data");
   }
 
   base::Time time{base::Time::FromTimeT(expiration)};
   if (time < clock_->Now()) {
-    Error::AddTo(error, FROM_HERE, errors::kAuthorizationExpired,
-                 "Token is expired");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kAuthorizationExpired,
+                        "Token is expired");
   }
 
   if (user_info)
@@ -329,8 +324,7 @@
                      return auth.first->IsValidAuthToken(token, nullptr);
                    });
   if (claim == pending_claims_.end()) {
-    Error::AddTo(error, FROM_HERE, errors::kNotFound, "Unknown claim");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kNotFound, "Unknown claim");
   }
 
   SetAuthSecret(claim->first->GetAuthSecret(), claim->second);
@@ -358,8 +352,8 @@
   UwMacaroon macaroon{};
   if (!LoadMacaroon(token, &buffer, &macaroon, error) ||
       !VerifyMacaroon(auth_secret_, macaroon, error)) {
-    Error::AddTo(error, FROM_HERE, errors::kInvalidAuthCode, "Invalid token");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kInvalidAuthCode,
+                        "Invalid token");
   }
   return true;
 }
diff --git a/src/privet/cloud_delegate.cc b/src/privet/cloud_delegate.cc
index 0eb04e0..5f31fee 100644
--- a/src/privet/cloud_delegate.cc
+++ b/src/privet/cloud_delegate.cc
@@ -320,9 +320,8 @@
       return true;
     }
 
-    Error::AddTo(error, FROM_HERE, errors::kAccessDenied,
-                 "Need to be owner of the command.");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kAccessDenied,
+                        "Need to be owner of the command.");
   }
 
   provider::TaskRunner* task_runner_{nullptr};
diff --git a/src/privet/privet_handler_unittest.cc b/src/privet/privet_handler_unittest.cc
index a353a0f..fa79e77 100644
--- a/src/privet/privet_handler_unittest.cc
+++ b/src/privet/privet_handler_unittest.cc
@@ -197,11 +197,9 @@
 TEST_F(PrivetHandlerTest, ExpiredAuth) {
   auth_header_ = "Privet 123";
   EXPECT_CALL(security_, ParseAccessToken(_, _, _))
-      .WillRepeatedly(DoAll(WithArgs<2>(Invoke([](ErrorPtr* error) {
-                              Error::AddTo(error, FROM_HERE,
-                                           "authorizationExpired", "");
-                            })),
-                            Return(false)));
+      .WillRepeatedly(WithArgs<2>(Invoke([](ErrorPtr* error) {
+        return Error::AddTo(error, FROM_HERE, "authorizationExpired", "");
+      })));
   EXPECT_PRED2(IsEqualError, CodeWithReason(403, "authorizationExpired"),
                HandleRequest("/privet/info", "{}"));
 }
@@ -379,10 +377,10 @@
 
 TEST_F(PrivetHandlerTest, AuthErrorInvalidAuthCode) {
   auto set_error = [](ErrorPtr* error) {
-    Error::AddTo(error, FROM_HERE, "invalidAuthCode", "");
+    return Error::AddTo(error, FROM_HERE, "invalidAuthCode", "");
   };
   EXPECT_CALL(security_, CreateAccessToken(_, "testToken", _, _, _, _, _))
-      .WillRepeatedly(DoAll(WithArgs<6>(Invoke(set_error)), Return(false)));
+      .WillRepeatedly(WithArgs<6>(Invoke(set_error)));
   const char kInput[] = R"({
     'mode': 'pairing',
     'requestedScope': 'user',
@@ -601,10 +599,9 @@
     }
   })";
   auto set_error = [](const std::string&, const std::string&, ErrorPtr* error) {
-    Error::AddTo(error, FROM_HERE, "deviceBusy", "");
+    return Error::AddTo(error, FROM_HERE, "deviceBusy", "");
   };
-  EXPECT_CALL(wifi_, ConfigureCredentials(_, _, _))
-      .WillOnce(DoAll(Invoke(set_error), Return(false)));
+  EXPECT_CALL(wifi_, ConfigureCredentials(_, _, _)).WillOnce(Invoke(set_error));
   EXPECT_PRED2(IsEqualError, CodeWithReason(503, "deviceBusy"),
                HandleRequest("/privet/v3/setup/start", kInput));
 
@@ -641,10 +638,9 @@
   })";
 
   auto set_error = [](const std::string&, const std::string&, ErrorPtr* error) {
-    Error::AddTo(error, FROM_HERE, "deviceBusy", "");
+    return Error::AddTo(error, FROM_HERE, "deviceBusy", "");
   };
-  EXPECT_CALL(cloud_, Setup(_, _, _))
-      .WillOnce(DoAll(Invoke(set_error), Return(false)));
+  EXPECT_CALL(cloud_, Setup(_, _, _)).WillOnce(Invoke(set_error));
   EXPECT_PRED2(IsEqualError, CodeWithReason(503, "deviceBusy"),
                HandleRequest("/privet/v3/setup/start", kInput));
 
@@ -857,8 +853,7 @@
           "{'path':'comp1.comp2', 'filter':['traits', 'components']}"));
 
   auto error_handler = [](ErrorPtr* error) -> const base::DictionaryValue* {
-    Error::AddTo(error, FROM_HERE, "componentNotFound", "");
-    return nullptr;
+    return Error::AddTo(error, FROM_HERE, "componentNotFound", "");
   };
   EXPECT_CALL(cloud_, FindComponent("comp7", _))
       .WillOnce(WithArgs<1>(Invoke(error_handler)));
diff --git a/src/privet/security_manager.cc b/src/privet/security_manager.cc
index 7a3533a..358876d 100644
--- a/src/privet/security_manager.cc
+++ b/src/privet/security_manager.cc
@@ -51,9 +51,8 @@
       case crypto::P224EncryptedKeyExchange::kResultPending:
         return true;
       case crypto::P224EncryptedKeyExchange::kResultFailed:
-        Error::AddTo(error, FROM_HERE, errors::kInvalidClientCommitment,
-                     spake_.error());
-        return false;
+        return Error::AddTo(error, FROM_HERE, errors::kInvalidClientCommitment,
+                            spake_.error());
       default:
         LOG(FATAL) << "SecurityManager uses only one round trip";
     }
@@ -139,9 +138,8 @@
     base::TimeDelta* access_token_ttl,
     ErrorPtr* error) {
   auto disabled_mode = [](ErrorPtr* error) {
-    Error::AddTo(error, FROM_HERE, errors::kInvalidAuthMode,
-                 "Mode is not available");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kInvalidAuthMode,
+                        "Mode is not available");
   };
 
   switch (auth_type) {
@@ -154,9 +152,8 @@
       if (!IsPairingAuthSupported())
         return disabled_mode(error);
       if (!IsValidPairingCode(auth_code)) {
-        Error::AddTo(error, FROM_HERE, errors::kInvalidAuthCode,
-                     "Invalid authCode");
-        return false;
+        return Error::AddTo(error, FROM_HERE, errors::kInvalidAuthCode,
+                            "Invalid authCode");
       }
       return CreateAccessTokenImpl(auth_type, desired_scope, access_token,
                                    access_token_scope, access_token_ttl);
@@ -170,9 +167,8 @@
           error);
   }
 
-  Error::AddTo(error, FROM_HERE, errors::kInvalidAuthMode,
-               "Unsupported auth mode");
-  return false;
+  return Error::AddTo(error, FROM_HERE, errors::kInvalidAuthMode,
+                      "Unsupported auth mode");
 }
 
 bool SecurityManager::CreateAccessToken(AuthType auth_type,
@@ -290,9 +286,8 @@
   const auto& pairing_modes = GetSettings().pairing_modes;
   if (std::find(pairing_modes.begin(), pairing_modes.end(), mode) ==
       pairing_modes.end()) {
-    Error::AddTo(error, FROM_HERE, errors::kInvalidParams,
-                 "Pairing mode is not enabled");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kInvalidParams,
+                        "Pairing mode is not enabled");
   }
 
   std::string code;
@@ -305,9 +300,8 @@
       code = base::StringPrintf("%04i", base::RandInt(0, 9999));
       break;
     default:
-      Error::AddTo(error, FROM_HERE, errors::kInvalidParams,
-                   "Unsupported pairing mode");
-      return false;
+      return Error::AddTo(error, FROM_HERE, errors::kInvalidParams,
+                          "Unsupported pairing mode");
   }
 
   std::unique_ptr<KeyExchanger> spake;
@@ -322,9 +316,8 @@
       }
     // Fall through...
     default:
-      Error::AddTo(error, FROM_HERE, errors::kInvalidParams,
-                   "Unsupported crypto");
-      return false;
+      return Error::AddTo(error, FROM_HERE, errors::kInvalidParams,
+                          "Unsupported crypto");
   }
 
   // Allow only a single session at a time for now.
@@ -382,9 +375,8 @@
   if (!session->second->ProcessMessage(
           std::string(commitment.begin(), commitment.end()), error)) {
     ClosePendingSession(session_id);
-    Error::AddTo(error, FROM_HERE, errors::kCommitmentMismatch,
-                 "Pairing code or crypto implementation mismatch");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kCommitmentMismatch,
+                        "Pairing code or crypto implementation mismatch");
   }
 
   const std::string& key = session->second->GetKey();
@@ -440,9 +432,8 @@
     return true;
 
   if (block_pairing_until_ > auth_manager_->Now()) {
-    Error::AddTo(error, FROM_HERE, errors::kDeviceBusy,
-                 "Too many pairing attempts");
-    return false;
+    return Error::AddTo(error, FROM_HERE, errors::kDeviceBusy,
+                        "Too many pairing attempts");
   }
 
   if (++pairing_attemts_ >= kMaxAllowedPairingAttemts) {
diff --git a/third_party/chromium/base/compiler_specific.h b/third_party/chromium/base/compiler_specific.h
index 339e9b7..79b7fa8 100644
--- a/third_party/chromium/base/compiler_specific.h
+++ b/third_party/chromium/base/compiler_specific.h
@@ -135,7 +135,7 @@
 // |dots_param| is the one-based index of the "..." parameter.
 // For v*printf functions (which take a va_list), pass 0 for dots_param.
 // (This is undocumented but matches what the system C headers do.)
-#if defined(COMPILER_GCC)
+#if defined(COMPILER_GCC) || defined(__clang__)
 #define PRINTF_FORMAT(format_param, dots_param) \
     __attribute__((format(printf, format_param, dots_param)))
 #else