diff --git a/buffet/commands/command_instance_unittest.cc b/buffet/commands/command_instance_unittest.cc
index 844ac92..1afd8c7 100644
--- a/buffet/commands/command_instance_unittest.cc
+++ b/buffet/commands/command_instance_unittest.cc
@@ -65,8 +65,8 @@
   buffet::native_types::Object params;
   buffet::IntPropType int_prop;
   buffet::DoublePropType dbl_prop;
-  params.insert(std::make_pair("freq", dbl_prop.CreateValue(800.5)));
-  params.insert(std::make_pair("volume", int_prop.CreateValue(100)));
+  params.insert(std::make_pair("freq", dbl_prop.CreateValue(800.5, nullptr)));
+  params.insert(std::make_pair("volume", int_prop.CreateValue(100, nullptr)));
   buffet::CommandInstance instance("robot._beep", "robotd", params);
 
   EXPECT_EQ("", instance.GetID());
diff --git a/buffet/commands/object_schema_unittest.cc b/buffet/commands/object_schema_unittest.cc
index e2e32e1..e802a67 100644
--- a/buffet/commands/object_schema_unittest.cc
+++ b/buffet/commands/object_schema_unittest.cc
@@ -14,6 +14,7 @@
 
 #include "buffet/commands/object_schema.h"
 #include "buffet/commands/prop_types.h"
+#include "buffet/commands/schema_constants.h"
 #include "buffet/commands/unittest_utils.h"
 
 using buffet::unittests::CreateValue;
@@ -124,6 +125,20 @@
   EXPECT_EQ("type_mismatch", error->GetCode());
 }
 
+TEST(CommandSchema, IntPropType_CreateValue) {
+  buffet::IntPropType prop;
+  chromeos::ErrorPtr error;
+  auto val = prop.CreateValue(2, &error);
+  ASSERT_NE(nullptr, val.get());
+  EXPECT_EQ(nullptr, error.get());
+  EXPECT_EQ(2, val->GetValueAsAny().Get<int>());
+
+  val = prop.CreateValue("blah", &error);
+  EXPECT_EQ(nullptr, val.get());
+  ASSERT_NE(nullptr, error.get());
+  EXPECT_EQ(buffet::errors::commands::kTypeMismatch, error->GetCode());
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 TEST(CommandSchema, BoolPropType_Empty) {
@@ -188,6 +203,20 @@
   EXPECT_EQ("type_mismatch", error->GetCode());
 }
 
+TEST(CommandSchema, BoolPropType_CreateValue) {
+  buffet::BooleanPropType prop;
+  chromeos::ErrorPtr error;
+  auto val = prop.CreateValue(true, &error);
+  ASSERT_NE(nullptr, val.get());
+  EXPECT_EQ(nullptr, error.get());
+  EXPECT_TRUE(val->GetValueAsAny().Get<bool>());
+
+  val = prop.CreateValue("blah", &error);
+  EXPECT_EQ(nullptr, val.get());
+  ASSERT_NE(nullptr, error.get());
+  EXPECT_EQ(buffet::errors::commands::kTypeMismatch, error->GetCode());
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 TEST(CommandSchema, DoublePropType_Empty) {
@@ -285,6 +314,20 @@
   EXPECT_EQ("type_mismatch", error->GetCode());
 }
 
+TEST(CommandSchema, DoublePropType_CreateValue) {
+  buffet::DoublePropType prop;
+  chromeos::ErrorPtr error;
+  auto val = prop.CreateValue(2.0, &error);
+  ASSERT_NE(nullptr, val.get());
+  EXPECT_EQ(nullptr, error.get());
+  EXPECT_DOUBLE_EQ(2.0, val->GetValueAsAny().Get<double>());
+
+  val = prop.CreateValue("blah", &error);
+  EXPECT_EQ(nullptr, val.get());
+  ASSERT_NE(nullptr, error.get());
+  EXPECT_EQ(buffet::errors::commands::kTypeMismatch, error->GetCode());
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 TEST(CommandSchema, StringPropType_Empty) {
@@ -388,6 +431,20 @@
   error.reset();
 }
 
+TEST(CommandSchema, StringPropType_CreateValue) {
+  buffet::StringPropType prop;
+  chromeos::ErrorPtr error;
+  auto val = prop.CreateValue(std::string{"blah"}, &error);
+  ASSERT_NE(nullptr, val.get());
+  EXPECT_EQ(nullptr, error.get());
+  EXPECT_EQ("blah", val->GetValueAsAny().Get<std::string>());
+
+  val = prop.CreateValue(4, &error);
+  EXPECT_EQ(nullptr, val.get());
+  ASSERT_NE(nullptr, error.get());
+  EXPECT_EQ(buffet::errors::commands::kTypeMismatch, error->GetCode());
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 TEST(CommandSchema, ObjectPropType_Empty) {
@@ -501,6 +558,30 @@
   error.reset();
 }
 
+TEST(CommandSchema, ObjectPropType_CreateValue) {
+  buffet::ObjectPropType prop;
+  buffet::IntPropType int_type;
+  ASSERT_TRUE(prop.FromJson(CreateDictionaryValue(
+      "{'properties':{'width':'integer','height':'integer'},"
+      "'enum':[{'width':10,'height':20},{'width':100,'height':200}]}").get(),
+      nullptr, nullptr));
+  buffet::native_types::Object obj{
+    {"width", int_type.CreateValue(10, nullptr)},
+    {"height", int_type.CreateValue(20, nullptr)},
+  };
+
+  chromeos::ErrorPtr error;
+  auto val = prop.CreateValue(obj, &error);
+  ASSERT_NE(nullptr, val.get());
+  EXPECT_EQ(nullptr, error.get());
+  EXPECT_EQ(obj, val->GetValueAsAny().Get<buffet::native_types::Object>());
+
+  val = prop.CreateValue("blah", &error);
+  EXPECT_EQ(nullptr, val.get());
+  ASSERT_NE(nullptr, error.get());
+  EXPECT_EQ(buffet::errors::commands::kTypeMismatch, error->GetCode());
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 TEST(CommandSchema, ObjectSchema_FromJson_Shorthand_TypeName) {
diff --git a/buffet/commands/prop_types.cc b/buffet/commands/prop_types.cc
index 81c9546..08410cc 100644
--- a/buffet/commands/prop_types.cc
+++ b/buffet/commands/prop_types.cc
@@ -152,9 +152,8 @@
 
 bool PropType::ValidateValue(const chromeos::Any& value,
                              chromeos::ErrorPtr* error) const {
-  std::shared_ptr<PropValue> val = CreateValue(value);
-  CHECK(val) << "Failed to create value object";
-  return ValidateConstraints(*val, error);
+  std::shared_ptr<PropValue> val = CreateValue(value, error);
+  return val && ValidateConstraints(*val, error);
 }
 
 bool PropType::ValidateConstraints(const PropValue& value,
@@ -218,6 +217,14 @@
   return std::unique_ptr<PropType>(prop);
 }
 
+bool PropType::GenerateErrorValueTypeMismatch(chromeos::ErrorPtr* error) const {
+  chromeos::Error::AddToPrintf(error, errors::commands::kDomain,
+                                errors::commands::kTypeMismatch,
+                                "Unable to convert value to type '%s'",
+                                GetTypeAsString().c_str());
+  return false;
+}
+
 template<typename T>
 static std::shared_ptr<Constraint> LoadOneOfConstraint(
     const base::DictionaryValue* value, const ObjectSchema* object_schema,
diff --git a/buffet/commands/prop_types.h b/buffet/commands/prop_types.h
index 3320202..2533c34 100644
--- a/buffet/commands/prop_types.h
+++ b/buffet/commands/prop_types.h
@@ -83,7 +83,7 @@
   // type as a factory class.
   virtual std::shared_ptr<PropValue> CreateValue() const = 0;
   virtual std::shared_ptr<PropValue> CreateValue(
-      const chromeos::Any& val) const = 0;
+      const chromeos::Any& val, chromeos::ErrorPtr* error) const = 0;
 
   // Saves the parameter type definition as a JSON object.
   // If |full_schema| is set to true, the full type definition is saved,
@@ -163,6 +163,10 @@
   bool ValidateConstraints(const PropValue& value,
                            chromeos::ErrorPtr* error) const;
 
+  // Helper method to generate "type mismatch" error when creating a value
+  // from this type. Always returns false.
+  bool GenerateErrorValueTypeMismatch(chromeos::ErrorPtr* error) const;
+
  protected:
   // Specifies if this parameter definition is derived from a base
   // object schema.
@@ -190,10 +194,16 @@
     return std::make_shared<Value>(this);
   }
   std::shared_ptr<PropValue> CreateValue(
-      const chromeos::Any& v) const override {
-    auto value = std::make_shared<Value>(this);
-    value->SetValue(v.Get<T>());
-    return std::move(value);
+      const chromeos::Any& v, chromeos::ErrorPtr* error) const override {
+    std::shared_ptr<PropValue> prop_value;
+    if (v.IsTypeCompatible<T>()) {
+      auto value = std::make_shared<Value>(this);
+      value->SetValue(v.Get<T>());
+      prop_value = std::move(value);
+    } else {
+      GenerateErrorValueTypeMismatch(error);
+    }
+    return prop_value;
   }
   bool ConstraintsFromJson(const base::DictionaryValue* value,
                            std::set<std::string>* processed_keys,
diff --git a/buffet/commands/schema_utils_unittest.cc b/buffet/commands/schema_utils_unittest.cc
index 1a92d7f..f3279be 100644
--- a/buffet/commands/schema_utils_unittest.cc
+++ b/buffet/commands/schema_utils_unittest.cc
@@ -56,8 +56,8 @@
   buffet::IntPropType int_type;
   buffet::native_types::Object object;
 
-  object.insert(std::make_pair("width", int_type.CreateValue(640)));
-  object.insert(std::make_pair("height", int_type.CreateValue(480)));
+  object.insert(std::make_pair("width", int_type.CreateValue(640, nullptr)));
+  object.insert(std::make_pair("height", int_type.CreateValue(480, nullptr)));
   EXPECT_EQ("{'height':480,'width':640}",
             ValueToString(buffet::TypedValueToJson(object, nullptr).get()));
 }
@@ -167,9 +167,10 @@
   EXPECT_TRUE(buffet::TypedValueFromJson(
       CreateValue("{'age':20,'name':'Bob'}").get(), &schema, &value, nullptr));
   buffet::native_types::Object value2;
-  value2.insert(std::make_pair("age", age_prop->CreateValue(20)));
+  value2.insert(std::make_pair("age", age_prop->CreateValue(20, nullptr)));
   value2.insert(std::make_pair("name",
-                               name_prop->CreateValue(std::string("Bob"))));
+                               name_prop->CreateValue(std::string("Bob"),
+                                                      nullptr)));
   EXPECT_EQ(value2, value);
 
   chromeos::ErrorPtr error;