diff --git a/netwerk/protocol/http/src/nsHttpResponseHead.h b/netwerk/protocol/http/src/nsHttpResponseHead.h
index 09038761d9d7..7bc3759cbcab 100644
--- a/netwerk/protocol/http/src/nsHttpResponseHead.h
+++ b/netwerk/protocol/http/src/nsHttpResponseHead.h
@@ -54,7 +54,7 @@ public:
     nsresult GetHeader(nsHttpAtom h, char **v)      { return mHeaders.GetHeader(h, v); }
     void     ClearHeaders()                         { mHeaders.Clear(); }
 
-    nsresult SetContentType(const char *s) { mContentType = s; }
+    nsresult SetContentType(const char *s) { mContentType = s; return NS_OK; }
 
     // write out the response status line and headers as a single text block,
     // optionally pruning out transient headers (ie. headers that only make