diff --git a/src/hb-buffer.h b/src/hb-buffer.h
index d1772d4..7b8b7ea 100644
--- a/src/hb-buffer.h
+++ b/src/hb-buffer.h
@@ -101,7 +101,7 @@
 void
 hb_buffer_clear_positions (hb_buffer_t *buffer);
 
-void
+hb_bool_t
 hb_buffer_ensure (hb_buffer_t  *buffer,
 		  unsigned int  size);