diff --git a/src/hb-aat-layout-morx-table.hh b/src/hb-aat-layout-morx-table.hh
index 15c03dbe6..b9fabe2b1 100644
--- a/src/hb-aat-layout-morx-table.hh
+++ b/src/hb-aat-layout-morx-table.hh
@@ -736,7 +736,7 @@ struct InsertionSubtable
 	if (unlikely (!buffer->move_to (mark))) return;
 
 	if (buffer->idx < buffer->len && !before)
-	  buffer->copy_glyph ();
+	  if (unlikely (!buffer->copy_glyph ())) return;
 	/* TODO We ignore KashidaLike setting. */
 	for (unsigned int i = 0; i < count; i++)
 	  buffer->output_glyph (glyphs[i]);
@@ -764,7 +764,7 @@ struct InsertionSubtable
 	unsigned int end = buffer->out_len;
 
 	if (buffer->idx < buffer->len && !before)
-	  buffer->copy_glyph ();
+	  if (unlikely (!buffer->copy_glyph ())) return;
 	/* TODO We ignore KashidaLike setting. */
 	for (unsigned int i = 0; i < count; i++)
 	  buffer->output_glyph (glyphs[i]);
diff --git a/src/hb-buffer.hh b/src/hb-buffer.hh
index 2e43f2e69..7ee204496 100644
--- a/src/hb-buffer.hh
+++ b/src/hb-buffer.hh
@@ -252,7 +252,7 @@ struct hb_buffer_t
     return true;
   }
   /* Copies glyph at idx to output but doesn't advance idx */
-  bool copy_glyph ()
+  HB_NODISCARD bool copy_glyph ()
   {
     if (unlikely (!make_room_for (0, 1))) return false;