diff --git a/src/hb-map.h b/src/hb-map.h
index 0f2b78a02..e928628fa 100644
--- a/src/hb-map.h
+++ b/src/hb-map.h
@@ -32,6 +32,7 @@
 #define HB_MAP_H
 
 #include "hb-common.h"
+#include "hb-set.h"
 
 HB_BEGIN_DECLS