diff --git a/src/hb-wasm-api-blob.hh b/src/hb-wasm-api-blob.hh
index 26b022bc3..310f4023f 100644
--- a/src/hb-wasm-api-blob.hh
+++ b/src/hb-wasm-api-blob.hh
@@ -34,7 +34,7 @@ namespace wasm {
 HB_WASM_API (void, blob_free) (HB_WASM_EXEC_ENV
 			       ptr_d(blob_t, blob))
 {
-  HB_OUT_PARAM (blob_t, blob);
+  HB_PTR_PARAM (blob_t, blob);
   if (unlikely (!blob))
     return;
 
diff --git a/src/hb-wasm-api-buffer.hh b/src/hb-wasm-api-buffer.hh
index 1d9612e88..7cfdb62f6 100644
--- a/src/hb-wasm-api-buffer.hh
+++ b/src/hb-wasm-api-buffer.hh
@@ -39,7 +39,7 @@ HB_WASM_API (void, buffer_contents_realloc) (HB_WASM_EXEC_ENV
 					     ptr_d(buffer_contents_t, contents),
 					     uint32_t size)
 {
-  HB_OUT_PARAM (buffer_contents_t, contents);
+  HB_PTR_PARAM (buffer_contents_t, contents);
   if (unlikely (!contents))
     return;
 
@@ -69,7 +69,7 @@ HB_WASM_API (void, buffer_contents_realloc) (HB_WASM_EXEC_ENV
 HB_WASM_API (void, buffer_contents_free) (HB_WASM_EXEC_ENV
 					  ptr_d(buffer_contents_t, contents))
 {
-  HB_OUT_PARAM (buffer_contents_t, contents);
+  HB_PTR_PARAM (buffer_contents_t, contents);
   if (unlikely (!contents))
     return;
 
@@ -101,7 +101,7 @@ HB_WASM_API (bool_t, buffer_set_contents) (HB_WASM_EXEC_ENV
 					   ptr_d(const buffer_contents_t, contents))
 {
   HB_REF2OBJ (buffer);
-  HB_OUT_PARAM (buffer_contents_t, contents);
+  HB_PTR_PARAM (buffer_contents_t, contents);
   if (unlikely (!contents))
     return false;
 
diff --git a/src/hb-wasm-api-font.hh b/src/hb-wasm-api-font.hh
index e5a6ff7fd..e3e5453d7 100644
--- a/src/hb-wasm-api-font.hh
+++ b/src/hb-wasm-api-font.hh
@@ -49,8 +49,8 @@ HB_WASM_API (void, font_get_scale) (HB_WASM_EXEC_ENV
 {
   HB_REF2OBJ (font);
 
-  HB_OUT_PARAM(int32_t, x_scale);
-  HB_OUT_PARAM(int32_t, y_scale);
+  HB_PTR_PARAM(int32_t, x_scale);
+  HB_PTR_PARAM(int32_t, y_scale);
 
   hb_font_get_scale (font, x_scale, y_scale);
 }
@@ -91,7 +91,7 @@ HB_WASM_API (bool_t, font_get_glyph_extents) (HB_WASM_EXEC_ENV
 					      ptr_d(glyph_extents_t, extents))
 {
   HB_REF2OBJ (font);
-  HB_OUT_PARAM (glyph_extents_t, extents);
+  HB_PTR_PARAM (glyph_extents_t, extents);
   if (unlikely (!extents))
     return false;
 
diff --git a/src/hb-wasm-api-list.hh b/src/hb-wasm-api-list.hh
index 0ded35980..8d05f2914 100644
--- a/src/hb-wasm-api-list.hh
+++ b/src/hb-wasm-api-list.hh
@@ -80,7 +80,7 @@ static NativeSymbol _hb_wasm_native_symbols[] =
   NATIVE_SYMBOL ("(ii$*)",	font_glyph_to_string),
 
   /* shape */
-  NATIVE_SYMBOL ("(ii$)i",	shape_with),
+  NATIVE_SYMBOL ("(iiii$)i",	shape_with),
 
   /* debug */
 #ifdef HB_DEBUG_WASM
diff --git a/src/hb-wasm-api-shape.hh b/src/hb-wasm-api-shape.hh
index d141b3c69..7e12969f7 100644
--- a/src/hb-wasm-api-shape.hh
+++ b/src/hb-wasm-api-shape.hh
@@ -31,19 +31,29 @@ namespace hb {
 namespace wasm {
 
 
+static_assert (sizeof (feature_t) == sizeof (hb_feature_t), "");
+
 HB_WASM_INTERFACE (bool_t, shape_with) (HB_WASM_EXEC_ENV
 				        ptr_d(font_t, font),
 				        ptr_d(buffer_t, buffer),
+				        ptr_d(const feature_t, features),
+				        uint32_t num_features,
 					const char *shaper)
 {
+  if (unlikely (0 == strcmp (shaper, "wasm")))
+    return false;
+
   HB_REF2OBJ (font);
   HB_REF2OBJ (buffer);
 
-  if (0 == strcmp (shaper, "wasm"))
+  HB_ARRAY_PARAM (const feature_t, features, num_features);
+  if (unlikely (!features && num_features))
     return false;
 
   const char * shaper_list[] = {shaper, nullptr};
-  return hb_shape_full (font, buffer, nullptr, 0, shaper_list);
+  return hb_shape_full (font, buffer,
+			(hb_feature_t *) features, num_features,
+			shaper_list);
 }
 
 
diff --git a/src/hb-wasm-api.h b/src/hb-wasm-api.h
index a59b405a4..acfe69a11 100644
--- a/src/hb-wasm-api.h
+++ b/src/hb-wasm-api.h
@@ -225,17 +225,29 @@ HB_WASM_API (void, font_glyph_to_string) (HB_WASM_EXEC_ENV
 
 /* shape */
 
+typedef struct {
+  tag_t    tag;
+  uint32_t value;
+  uint32_t start;
+  uint32_t end;
+} feature_t;
+#define FEATURE_GLOBAL_START	0
+#define FEATURE_GLOBAL_END	((uint32_t) -1)
+
 HB_WASM_INTERFACE (bool_t, shape_with) (HB_WASM_EXEC_ENV
 				        ptr_d(font_t, font),
 				        ptr_d(buffer_t, buffer),
+				        ptr_d(const feature_t, features),
+				        uint32_t num_features,
 					const char *shaper);
 
-
-/* shape interface */
+/* Implement this in your shaper. */
 
 HB_WASM_INTERFACE (bool_t, shape) (HB_WASM_EXEC_ENV
 				   ptr_d(font_t, font),
-				   ptr_d(buffer_t, buffer));
+				   ptr_d(buffer_t, buffer),
+				   ptr_d(const feature_t, features),
+				   uint32_t num_features);
 
 
 HB_WASM_END_DECLS
diff --git a/src/hb-wasm-api.hh b/src/hb-wasm-api.hh
index f5ef9e487..f7e5565be 100644
--- a/src/hb-wasm-api.hh
+++ b/src/hb-wasm-api.hh
@@ -91,7 +91,7 @@ HB_INTERNAL extern hb_user_data_key_t _hb_wasm_ref_type_key;
   } \
   type &name = *_name_ptr
 
-#define HB_OUT_PARAM(type, name) \
+#define HB_PTR_PARAM(type, name) \
   type *name = nullptr; \
   HB_STMT_START { \
     if (likely (wasm_runtime_validate_app_addr (module_inst, \
@@ -99,5 +99,14 @@ HB_INTERNAL extern hb_user_data_key_t _hb_wasm_ref_type_key;
       name = (type *) wasm_runtime_addr_app_to_native (module_inst, name##ptr); \
   } HB_STMT_END
 
+#define HB_ARRAY_PARAM(type, name, length) \
+  type *name = nullptr; \
+  HB_STMT_START { \
+    if (likely (!hb_unsigned_mul_overflows (length, sizeof (type)) && \
+		wasm_runtime_validate_app_addr (module_inst, \
+						name##ptr, length * sizeof (type)))) \
+      name = (type *) wasm_runtime_addr_app_to_native (module_inst, name##ptr); \
+  } HB_STMT_END
+
 
 #endif /* HB_WASM_API_HH */
diff --git a/src/hb-wasm-shape.cc b/src/hb-wasm-shape.cc
index 4fe2ab511..317fb9cf0 100644
--- a/src/hb-wasm-shape.cc
+++ b/src/hb-wasm-shape.cc
@@ -197,17 +197,27 @@ _hb_wasm_shape (hb_shape_plan_t    *shape_plan,
   }
 
   wasm_val_t results[1];
-  wasm_val_t arguments[2];
+  wasm_val_t arguments[4];
 
   results[0].kind = WASM_I32;
   arguments[0].kind = WASM_I32;
   arguments[0].of.i32 = fontref;
   arguments[1].kind = WASM_I32;
   arguments[1].of.i32 = bufferref;
+  arguments[2].kind = WASM_I32;
+  arguments[2].of.i32 = wasm_runtime_module_dup_data (module_inst,
+						      (const char *) features,
+						      num_features * sizeof (features[0]));
+  arguments[3].kind = WASM_I32;
+  arguments[3].of.i32 = num_features;
 
    ret = wasm_runtime_call_wasm_a (exec_env, shape_func,
 				   ARRAY_LENGTH (results), results,
 				   ARRAY_LENGTH (arguments), arguments);
+
+
+  wasm_runtime_module_free (module_inst, arguments[2].of.i32);
+
   if (unlikely (!ret))
   {
     DEBUG_MSG (WASM, module_inst, "Calling shape function failed: %s",
diff --git a/src/wasm-graphite/shape.cc b/src/wasm-graphite/shape.cc
index e1a863b10..a1f140867 100644
--- a/src/wasm-graphite/shape.cc
+++ b/src/wasm-graphite/shape.cc
@@ -36,7 +36,10 @@ static void free_table (const void *data, const void *table_data)
 }
 
 bool_t
-shape (font_t *font, buffer_t *buffer)
+shape (font_t *font,
+       buffer_t *buffer,
+       const feature_t *features,
+       uint32_t num_features)
 {
   direction_t direction = buffer_get_direction (buffer);
   direction_t horiz_dir = script_get_horizontal_direction (buffer_get_script (buffer));
diff --git a/src/wasm-sample/shape-fallback.cc b/src/wasm-sample/shape-fallback.cc
index 11853c402..ecb90d030 100644
--- a/src/wasm-sample/shape-fallback.cc
+++ b/src/wasm-sample/shape-fallback.cc
@@ -9,7 +9,10 @@ void debugprint2 (const char *s, int32_t, int32_t);
 }
 
 bool_t
-shape (font_t *font, buffer_t *buffer)
+shape (font_t *font,
+       buffer_t *buffer,
+       const feature_t *features,
+       uint32_t num_features)
 {
   face_t *face = font_get_face (font);
 
diff --git a/src/wasm-sample/shape-ot.cc b/src/wasm-sample/shape-ot.cc
index 10e1e723d..98276ec49 100644
--- a/src/wasm-sample/shape-ot.cc
+++ b/src/wasm-sample/shape-ot.cc
@@ -8,7 +8,10 @@ void debugprint2 (const char *s, int32_t, int32_t);
 }
 
 bool_t
-shape (font_t *font, buffer_t *buffer)
+shape (font_t *font,
+       buffer_t *buffer,
+       const feature_t *features,
+       uint32_t num_features)
 {
-  return shape_with (font, buffer, "ot");
+  return shape_with (font, buffer, features, num_features, "ot");
 }