diff --git a/xpcom/base/nscore.h b/xpcom/base/nscore.h
index 49af18c9de3e..969d7eaffdde 100644
--- a/xpcom/base/nscore.h
+++ b/xpcom/base/nscore.h
@@ -253,6 +253,7 @@ typedef PRUint16 PRUnichar;
 /* Because this may be included bogously a C file (or an extern "C"
    block), we'll "extern C++" it. There's a bug filed against that
    somewhere. */
+#ifdef __cplusplus
 extern "C++" {
 
 template <class T>
@@ -272,4 +273,6 @@ NS_MAX( const T& a, const T& b )
   }
 }
 
+#endif /* __cplusplus */
+
 #endif /* nscore_h___ */