diff --git a/xpcom/typelib/xpidl/xpidl_header.c b/xpcom/typelib/xpidl/xpidl_header.c
index 3195d36034a8..e941dc602c82 100644
--- a/xpcom/typelib/xpidl/xpidl_header.c
+++ b/xpcom/typelib/xpidl/xpidl_header.c
@@ -45,7 +45,7 @@ write_header(gpointer key, gpointer value, gpointer user_data)
     char *ident = (char *)value;
     TreeState *state = (TreeState *)user_data;
     fprintf(state->file, "#include \"%s.h\"\n",
-            ident, ident);
+            ident);
 }
 
 static gboolean