diff --git a/src/hb-uniscribe.cc b/src/hb-uniscribe.cc
index 1594948d6..6bf87a5f4 100644
--- a/src/hb-uniscribe.cc
+++ b/src/hb-uniscribe.cc
@@ -310,6 +310,7 @@ _hb_generate_unique_face_name (wchar_t *face_name, unsigned int *plen)
   const char *enc = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-";
   UUID id;
   UuidCreate ((UUID*) &id);
+  ASSERT_STATIC (2 + 3 * (16/2) < LF_FACESIZE);
   unsigned int name_str_len = 0;
   face_name[name_str_len++] = 'F';
   face_name[name_str_len++] = '_';