diff --git a/src/hb-buffer.hh b/src/hb-buffer.hh
index 5a43cabcb..d50641ef2 100644
--- a/src/hb-buffer.hh
+++ b/src/hb-buffer.hh
@@ -493,6 +493,13 @@ struct hb_buffer_t
 
   HB_NODISCARD HB_INTERNAL bool enlarge (unsigned int size);
 
+  HB_NODISCARD bool resize (unsigned length)
+  {
+    assert (!have_output);
+    if (unlikely (!ensure (length))) return false;
+    len = length;
+    return true;
+  }
   HB_NODISCARD bool ensure (unsigned int size)
   { return likely (!size || size < allocated) ? true : enlarge (size); }
 
diff --git a/src/hb-wasm-api-buffer.hh b/src/hb-wasm-api-buffer.hh
index 07d7ab418..3164b7617 100644
--- a/src/hb-wasm-api-buffer.hh
+++ b/src/hb-wasm-api-buffer.hh
@@ -32,6 +32,8 @@
 namespace hb {
 namespace wasm {
 
+static_assert (sizeof (glyph_info_t) == sizeof (hb_glyph_info_t), "");
+static_assert (sizeof (glyph_position_t) == sizeof (hb_glyph_position_t), "");
 
 void
 buffer_contents_free (HB_WASM_EXEC_ENV
@@ -59,9 +61,6 @@ buffer_copy_contents (HB_WASM_EXEC_ENV_COMPOUND
   if (buffer->have_output)
     buffer->sync ();
 
-  static_assert (sizeof (glyph_info_t) == sizeof (hb_glyph_info_t), "");
-  static_assert (sizeof (glyph_position_t) == sizeof (hb_glyph_position_t), "");
-
   unsigned length = buffer->len;
   ret.length = length;
   ret.info = wasm_runtime_module_dup_data (module_inst, (const char *) buffer->info, length * sizeof (buffer->info[0]));
@@ -69,6 +68,35 @@ buffer_copy_contents (HB_WASM_EXEC_ENV_COMPOUND
 }
 
 
+bool_t
+buffer_set_contents (HB_WASM_EXEC_ENV
+		     ptr_t(buffer_t) bufferref,
+		     ptr_t(const buffer_contents_t) contentsptr)
+{
+  HB_REF2OBJ (buffer);
+  HB_STRUCT_TYPE (buffer_contents_t, contents);
+  if (unlikely (!contents))
+    return false;
+
+  unsigned length = contents->length;
+  unsigned bytes;
+  if (unlikely (hb_unsigned_mul_overflows (length, sizeof (buffer->info[0]), &bytes)))
+    return false;
+
+  if (unlikely (!buffer->resize (length)))
+    return false;
+
+  glyph_info_t *info = (glyph_info_t *) (validate_app_addr (contents->info, bytes) ? addr_app_to_native (contents->info) : nullptr);
+  glyph_position_t *pos = (glyph_position_t *) (validate_app_addr (contents->pos, bytes) ? addr_app_to_native (contents->pos) : nullptr);
+
+  buffer->clear_positions (); /* This is wasteful, but we need it to set have_positions=true. */
+  memcpy (buffer->info, info, bytes);
+  memcpy (buffer->pos, pos, bytes);
+  buffer->len = length;
+
+  return true;
+}
+
 }}
 
 #endif /* HB_WASM_API_BUFFER_HH */
diff --git a/src/hb-wasm-api-list.hh b/src/hb-wasm-api-list.hh
index df39ad17b..dc29b2f8f 100644
--- a/src/hb-wasm-api-list.hh
+++ b/src/hb-wasm-api-list.hh
@@ -57,15 +57,16 @@ static NativeSymbol _hb_wasm_native_symbols[] =
   /* buffer */
   NATIVE_SYMBOL ("(i)",		buffer_contents_free),
   NATIVE_SYMBOL ("(ii)",	buffer_copy_contents),
+  NATIVE_SYMBOL ("(ii)i",	buffer_set_contents),
 
   /* face */
   NATIVE_SYMBOL ("(iii)",	face_reference_table),
 
   /* font */
-  NATIVE_SYMBOL ("(i)i",		font_get_face),
+  NATIVE_SYMBOL ("(i)i",	font_get_face),
   NATIVE_SYMBOL ("(iii)i",	font_get_glyph),
-  NATIVE_SYMBOL ("(ii)i",		font_get_glyph_h_advance),
-  NATIVE_SYMBOL ("(ii)i",		font_get_glyph_v_advance),
+  NATIVE_SYMBOL ("(ii)i",	font_get_glyph_h_advance),
+  NATIVE_SYMBOL ("(ii)i",	font_get_glyph_v_advance),
 
   /* debug */
 #ifdef HB_DEBUG_WASM
diff --git a/src/hb-wasm-api.h b/src/hb-wasm-api.h
index 66d5b64c0..e5f6700d1 100644
--- a/src/hb-wasm-api.h
+++ b/src/hb-wasm-api.h
@@ -123,6 +123,10 @@ typedef struct buffer_t buffer_t;
 HB_WASM_API_COMPOUND (buffer_contents_t, buffer_copy_contents) (HB_WASM_EXEC_ENV_COMPOUND
 								ptr_t(buffer_t));
 
+HB_WASM_API (bool_t, buffer_set_contents) (HB_WASM_EXEC_ENV
+					   ptr_t(buffer_t),
+					   ptr_t(const buffer_contents_t));
+
 
 /* face */
 
diff --git a/src/wasm-sample/shape.c b/src/wasm-sample/shape.c
index 80486b2b5..c558114c9 100644
--- a/src/wasm-sample/shape.c
+++ b/src/wasm-sample/shape.c
@@ -23,9 +23,15 @@ shape (font_t *font, buffer_t *buffer)
   debugprint1 ("buffer length", contents.length);
 
   for (unsigned i = 0; i < contents.length; i++)
+  {
     debugprint2 ("Codepoint", i, contents.info[i].codepoint);
+    contents.info[i].codepoint++;
+    contents.pos[i].x_advance = 256 * 64;
+  }
+
+  bool_t ret = buffer_set_contents (buffer, &contents);
 
   buffer_contents_free (&contents);
 
-  return 1;
+  return ret;
 }