diff --git a/test/api/test-shape.c b/test/api/test-shape.c
index eb244072a..c274f0f7e 100644
--- a/test/api/test-shape.c
+++ b/test/api/test-shape.c
@@ -101,7 +101,7 @@ test_shape (void)
 
   ffuncs = hb_font_funcs_create ();
   hb_font_funcs_set_glyph_h_advance_func (ffuncs, glyph_h_advance_func, NULL, NULL);
-  hb_font_funcs_set_glyph_func (ffuncs, glyph_func, NULL, NULL);
+  hb_font_funcs_set_glyph_func (ffuncs, glyph_func, malloc (10), free);
   hb_font_funcs_set_glyph_h_kerning_func (ffuncs, glyph_h_kerning_func, NULL, NULL);
   hb_font_set_funcs (font, ffuncs, NULL, NULL);
   hb_font_funcs_destroy (ffuncs);