--- a/toolkit/components/telemetry/TelemetryScalar.h
+++ b/toolkit/components/telemetry/TelemetryScalar.h
@@ -3,23 +3,31 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef TelemetryScalar_h__
 #define TelemetryScalar_h__
 
 #include "mozilla/TelemetryScalarEnums.h"
 #include "mozilla/TelemetryProcessEnums.h"
-#include "ipc/TelemetryComms.h"
 
 // This module is internal to Telemetry. It encapsulates Telemetry's
 // scalar accumulation and storage logic. It should only be used by
 // Telemetry.cpp. These functions should not be used anywhere else.
 // For the public interface to Telemetry functionality, see Telemetry.h.
 
+namespace mozilla {
+namespace Telemetry {
+  struct ScalarAction;
+  struct KeyedScalarAction;
+  struct DiscardedData;
+  struct DynamicScalarDefinition;
+} // namespace Telemetry
+} // namespace mozilla
+
 namespace TelemetryScalar {
 
 void InitializeGlobalState(bool canRecordBase, bool canRecordExtended);
 void DeInitializeGlobalState();
 
 void SetCanRecordBase(bool b);
 void SetCanRecordExtended(bool b);