diff --git a/buffet/commands/cloud_command_proxy.cc b/buffet/commands/cloud_command_proxy.cc
index 8aa27ba..d3cd5a6 100644
--- a/buffet/commands/cloud_command_proxy.cc
+++ b/buffet/commands/cloud_command_proxy.cc
@@ -7,6 +7,7 @@
 #include "buffet/commands/command_instance.h"
 #include "buffet/commands/prop_constraints.h"
 #include "buffet/commands/prop_types.h"
+#include "buffet/commands/schema_constants.h"
 #include "buffet/device_registration_info.h"
 
 namespace buffet {
@@ -20,20 +21,21 @@
 
 void CloudCommandProxy::OnResultsChanged(const native_types::Object& results) {
   base::DictionaryValue patch;
-  patch.Set("results", TypedValueToJson(results, nullptr).get());
+  patch.Set(commands::attributes::kCommand_Results,
+            TypedValueToJson(results, nullptr).get());
   device_registration_info_->UpdateCommand(command_instance_->GetID(), patch);
 }
 
 void CloudCommandProxy::OnStatusChanged(const std::string& status) {
   base::DictionaryValue patch;
   // TODO(antonm): Change status to state.
-  patch.SetString("state", status);
+  patch.SetString(commands::attributes::kCommand_State, status);
   device_registration_info_->UpdateCommand(command_instance_->GetID(), patch);
 }
 
 void CloudCommandProxy::OnProgressChanged(int progress) {
   base::DictionaryValue patch;
-  patch.SetInteger("progress", progress);
+  patch.SetInteger(commands::attributes::kCommand_Progress, progress);
   // TODO(antonm): Consider batching progress change updates.
   device_registration_info_->UpdateCommand(command_instance_->GetID(), patch);
 }