diff --git a/src/hb-ms-feature-ranges.hh b/src/hb-ms-feature-ranges.hh
index 5d9c659c0..d40fdeaa8 100644
--- a/src/hb-ms-feature-ranges.hh
+++ b/src/hb-ms-feature-ranges.hh
@@ -52,7 +52,7 @@ struct hb_ms_active_feature_t {
 	   a->fea.value < b->fea.value ? -1 : a->fea.value > b->fea.value ? 1 :
 	   0;
   }
-  bool operator== (const hb_ms_active_feature_t f) const
+  bool operator== (const hb_ms_active_feature_t& f) const
   { return cmp (this, &f) == 0; }
 };