diff --git a/src/hb-open-file.hh b/src/hb-open-file.hh
index 14519e1c2..317c49bbb 100644
--- a/src/hb-open-file.hh
+++ b/src/hb-open-file.hh
@@ -119,7 +119,7 @@ typedef struct OpenTypeOffsetTable
   public:
 
   template <typename Iterator,
-	    hb_requires (hb_is_iterator(Iterator))>
+	    hb_requires (hb_is_iterator (Iterator))>
   bool serialize (hb_serialize_context_t *c,
 		  hb_tag_t sfnt_tag,
 		  Iterator it)