diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index 7a0d026..8d09876 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -2000,17 +2000,21 @@
 void hb_ot_map_t::substitute (const hb_ot_shape_plan_t *plan, hb_font_t *font, hb_buffer_t *buffer) const
 {
   GSUBProxy proxy (font->face);
-  if (!buffer->message (font, "start table GSUB")) return;
+  if (buffer->messaging () &&
+      !buffer->message (font, "start table GSUB")) return;
   apply (proxy, plan, font, buffer);
-  (void) buffer->message (font, "end table GSUB");
+  if (buffer->messaging ())
+    (void) buffer->message (font, "end table GSUB");
 }
 
 void hb_ot_map_t::position (const hb_ot_shape_plan_t *plan, hb_font_t *font, hb_buffer_t *buffer) const
 {
   GPOSProxy proxy (font->face);
-  if (!buffer->message (font, "start table GPOS")) return;
+  if (buffer->messaging () &&
+      !buffer->message (font, "start table GPOS")) return;
   apply (proxy, plan, font, buffer);
-  (void) buffer->message (font, "end table GPOS");
+  if (buffer->messaging ())
+    (void) buffer->message (font, "end table GPOS");
 }
 
 void