diff --git a/src/hb-buffer-private.h b/src/hb-buffer-private.h
index 3a74f2e5b..dab403b80 100644
--- a/src/hb-buffer-private.h
+++ b/src/hb-buffer-private.h
@@ -102,10 +102,18 @@ HB_INTERNAL void
 _hb_buffer_add_output_glyphs (hb_buffer_t *buffer,
 			      unsigned int num_in,
 			      unsigned int num_out,
-			      const uint16_t *glyph_data_be,
+			      const hb_codepoint_t *glyph_data,
 			      unsigned short component,
 			      unsigned short ligID);
 
+HB_INTERNAL void
+_hb_buffer_add_output_glyphs_be16 (hb_buffer_t *buffer,
+				   unsigned int num_in,
+				   unsigned int num_out,
+				   const uint16_t *glyph_data_be,
+				   unsigned short component,
+				   unsigned short ligID);
+
 HB_INTERNAL void
 _hb_buffer_add_output_glyph (hb_buffer_t *buffer,
 			     hb_codepoint_t glyph_index,
diff --git a/src/hb-buffer.c b/src/hb-buffer.c
index 1e4867d9b..76b69c883 100644
--- a/src/hb-buffer.c
+++ b/src/hb-buffer.c
@@ -305,11 +305,12 @@ _hb_buffer_swap (hb_buffer_t *buffer)
 
    The cluster value for the glyph at position buffer->in_pos is used
    for all replacement glyphs */
+
 void
 _hb_buffer_add_output_glyphs (hb_buffer_t *buffer,
 			      unsigned int num_in,
 			      unsigned int num_out,
-			      const uint16_t *glyph_data_be,
+			      const hb_codepoint_t *glyph_data,
 			      unsigned short component,
 			      unsigned short lig_id)
 {
@@ -323,6 +324,47 @@ _hb_buffer_add_output_glyphs (hb_buffer_t *buffer,
     hb_buffer_ensure_separate (buffer, buffer->out_pos + num_out);
   }
 
+  mask = buffer->in_string[buffer->in_pos].mask;
+  cluster = buffer->in_string[buffer->in_pos].cluster;
+  if (component == 0xFFFF)
+    component = buffer->in_string[buffer->in_pos].component;
+  if (lig_id == 0xFFFF)
+    lig_id = buffer->in_string[buffer->in_pos].lig_id;
+
+  for (i = 0; i < num_out; i++)
+  {
+    hb_internal_glyph_info_t *info = &buffer->out_string[buffer->out_pos + i];
+    info->codepoint = glyph_data[i];
+    info->mask = mask;
+    info->cluster = cluster;
+    info->component = component;
+    info->lig_id = lig_id;
+    info->gproperty = HB_BUFFER_GLYPH_PROPERTIES_UNKNOWN;
+  }
+
+  buffer->in_pos  += num_in;
+  buffer->out_pos += num_out;
+  buffer->out_length = buffer->out_pos;
+}
+
+void
+_hb_buffer_add_output_glyphs_be16 (hb_buffer_t *buffer,
+				   unsigned int num_in,
+				   unsigned int num_out,
+				   const uint16_t *glyph_data_be,
+				   unsigned short component,
+				   unsigned short lig_id)
+{
+  unsigned int i;
+  unsigned int mask;
+  unsigned int cluster;
+
+  if (buffer->out_string != buffer->in_string ||
+      buffer->out_pos + num_out > buffer->in_pos + num_in)
+  {
+    hb_buffer_ensure_separate (buffer, buffer->out_pos + num_out);
+  }
+
   mask = buffer->in_string[buffer->in_pos].mask;
   cluster = buffer->in_string[buffer->in_pos].cluster;
   if (component == 0xFFFF)
@@ -346,7 +388,6 @@ _hb_buffer_add_output_glyphs (hb_buffer_t *buffer,
   buffer->out_length = buffer->out_pos;
 }
 
-
 void
 _hb_buffer_add_output_glyph (hb_buffer_t *buffer,
 			     hb_codepoint_t glyph_index,
diff --git a/src/hb-ot-layout-gsub-private.hh b/src/hb-ot-layout-gsub-private.hh
index eb74c033c..fd161c01d 100644
--- a/src/hb-ot-layout-gsub-private.hh
+++ b/src/hb-ot-layout-gsub-private.hh
@@ -158,9 +158,9 @@ struct Sequence
     if (HB_UNLIKELY (!substitute.len))
       return false;
 
-    _hb_buffer_add_output_glyphs (buffer, 1,
-				  substitute.len, (const uint16_t *) substitute.const_array(),
-				  0xFFFF, 0xFFFF);
+    _hb_buffer_add_output_glyphs_be16 (buffer, 1,
+				       substitute.len, (const uint16_t *) substitute.const_array(),
+				       0xFFFF, 0xFFFF);
 
     /* This is a guess only ... */
     if (_hb_ot_layout_has_new_glyph_classes (context->face))
@@ -386,11 +386,11 @@ struct Ligature
     if (j == buffer->in_pos + i) /* No input glyphs skipped */
       /* We don't use a new ligature ID if there are no skipped
 	 glyphs and the ligature already has an ID. */
-      _hb_buffer_add_output_glyphs (buffer, i,
-				    1, (const uint16_t *) &ligGlyph,
-				    0xFFFF,
-				    IN_LIGID (buffer->in_pos) ?
-				    0xFFFF : _hb_buffer_allocate_lig_id (buffer));
+      _hb_buffer_add_output_glyphs_be16 (buffer, i,
+					 1, (const uint16_t *) &ligGlyph,
+					 0xFFFF,
+					 IN_LIGID (buffer->in_pos) ?
+					 0xFFFF : _hb_buffer_allocate_lig_id (buffer));
     else
     {
       unsigned int lig_id = _hb_buffer_allocate_lig_id (buffer);