diff --git a/xpcom/base/nsIMemory.idl b/xpcom/base/nsIMemory.idl
index 887d0367a110..3d6bac70609b 100644
--- a/xpcom/base/nsIMemory.idl
+++ b/xpcom/base/nsIMemory.idl
@@ -143,3 +143,10 @@ interface nsIMemory : nsISupports
  */
 #define NS_MEMORY_PRESSURE_ALLOC_FAILURE (NS_LITERAL_STRING("alloc-failure").get())
 %}
+
+%{C++
+/**
+ * ContractID for the global memory service:
+ */
+#define NS_MEMORY_CONTRACTID "@mozilla.org/xpcom/memory-service;1"
+%}
diff --git a/xpcom/base/nsMemory.h b/xpcom/base/nsMemory.h
index d82b6b4a415a..15f52cf17da7 100644
--- a/xpcom/base/nsMemory.h
+++ b/xpcom/base/nsMemory.h
@@ -57,8 +57,7 @@ public:
     static NS_EXPORT nsIMemory* GetGlobalMemoryService();       // AddRefs
 };
 
-// ContractID/CID for the global memory service:
-#define NS_MEMORY_CONTRACTID        "@mozilla.org/xpcom/memory-service;1"
+// CID for the global memory service:
 #define NS_MEMORY_CLASSNAME     "Global Memory Service"
 #define NS_MEMORY_CID                                \
 { /* 30a04e40-38e7-11d4-8cf5-0060b0fc14a3 */         \