diff --git a/src/hb-ot-layout-gsub-table.hh b/src/hb-ot-layout-gsub-table.hh
index bdc7b38663be99572e7134d53de86aabbd4028b9..6a292a1e838c1d2fbcda5584ced8df5806fb956e 100644
--- a/src/hb-ot-layout-gsub-table.hh
+++ b/src/hb-ot-layout-gsub-table.hh
@@ -920,7 +920,7 @@ struct ReverseChainSingleSubstFormat1
 			 match_coverage, this,
 			 1))
     {
-      c->buffer->cur().codepoint = substitute[index];
+      c->replace_glyph_inplace (substitute[index]);
       c->buffer->idx--; /* Reverse! */
       return TRACE_RETURN (true);
     }
diff --git a/src/hb-ot-layout-gsubgpos-private.hh b/src/hb-ot-layout-gsubgpos-private.hh
index 6dc2f162ef4bcbc847f76e9a5d9234172c70b407..e2423bcd0331083a6b350d85dc8a92a4cc945b6f 100644
--- a/src/hb-ot-layout-gsubgpos-private.hh
+++ b/src/hb-ot-layout-gsubgpos-private.hh
@@ -246,6 +246,12 @@ struct hb_apply_context_t
     set_klass_guess (klass_guess);
     buffer->replace_glyph (glyph_index);
   }
+  inline void replace_glyph_inplace (hb_codepoint_t glyph_index,
+				     unsigned int klass_guess = 0) const
+  {
+    set_klass_guess (klass_guess);
+    buffer->cur().codepoint = glyph_index;
+  }
 };