diff --git a/xpcom/typelib/xpt/src/xpt_xdr.c b/xpcom/typelib/xpt/src/xpt_xdr.c
index 9da82e821e0..5c7ca9602d8 100644
--- a/xpcom/typelib/xpt/src/xpt_xdr.c
+++ b/xpcom/typelib/xpt/src/xpt_xdr.c
@@ -62,7 +62,7 @@ CheckForRepeat(XPTCursor *cursor, void **addrp, XPTPool pool, PRUint32 len,
   ((cursor)->state->pool->data[CURS_POOL_OFFSET(cursor)])
 
 #if defined(DEBUG_shaver) || defined(DEBUG_jband) || defined(DEBUG_mccabe)
-#define DBG(x) printf##x
+#define DBG(x) printf x
 #else
 #define DBG(x) (0)
 #endif