--- a/memory/replace/dmd/DMD.h
+++ b/memory/replace/dmd/DMD.h
@@ -74,27 +74,34 @@ private:
   // Wrapper class keeping a pointer to the DMD functions. It is statically
   // initialized because it needs to be set early enough.
   // Debug builds also check that it's never accessed before the static
   // initialization actually occured, which could be the case if some other
   // static initializer ended up calling into DMD.
   class Singleton
   {
   public:
-    Singleton() : mValue(ReplaceMalloc::GetDMDFuncs()), mInitialized(true) {}
+    Singleton()
+      : mValue(ReplaceMalloc::GetDMDFuncs())
+#ifdef DEBUG
+      , mInitialized(true)
+#endif
+    {}
 
     DMDFuncs* Get()
     {
       MOZ_ASSERT(mInitialized);
       return mValue;
     }
 
   private:
     DMDFuncs* mValue;
-    DebugOnly<bool> mInitialized;
+#ifdef DEBUG
+    bool mInitialized;
+#endif
   };
 
   // This singleton pointer must be defined on the program side. In Gecko,
   // this is done in xpcom/base/nsMemoryInfoDumper.cpp.
   static /* DMDFuncs:: */Singleton sSingleton;
 #endif
 };