diff --git a/src/hb-ot-layout-gsubgpos-private.hh b/src/hb-ot-layout-gsubgpos-private.hh
index 9471ad3c2..904c344f2 100644
--- a/src/hb-ot-layout-gsubgpos-private.hh
+++ b/src/hb-ot-layout-gsubgpos-private.hh
@@ -98,7 +98,7 @@ struct hb_closure_context_t
 #endif
 
 #define TRACE_APPLY() \
-	hb_auto_trace_t<HB_DEBUG_APPLY> trace (&c->debug_depth, "APPLY", this, HB_FUNC, "");
+	hb_auto_trace_t<HB_DEBUG_APPLY> trace (&c->debug_depth, "APPLY", this, HB_FUNC, "idx %d codepoint %u", c->buffer->idx, c->buffer->info[c->buffer->idx].codepoint);