diff --git a/src/hb-common.cc b/src/hb-common.cc
index 5b60ff4..ec463a9 100644
--- a/src/hb-common.cc
+++ b/src/hb-common.cc
@@ -69,6 +69,7 @@
 	if (0 == strncmp (c, name, p - c) && strlen (name) == static_cast<size_t>(p - c)) do { u.opts.symbol = true; } while (0)
 
       OPTION ("uniscribe-bug-compatible", uniscribe_bug_compatible);
+      OPTION ("aat", aat);
 
 #undef OPTION
 
diff --git a/src/hb-debug.hh b/src/hb-debug.hh
index 5c13e5d..8ecdf57 100644
--- a/src/hb-debug.hh
+++ b/src/hb-debug.hh
@@ -46,6 +46,7 @@
   bool unused : 1; /* In-case sign bit is here. */
   bool initialized : 1;
   bool uniscribe_bug_compatible : 1;
+  bool aat : 1;
 };
 
 union hb_options_union_t {
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index c165b1e..07a26ec 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -399,6 +399,27 @@
 #ifdef HB_NO_OT_LAYOUT_BLACKLIST
   return false;
 #endif
+
+#ifndef HB_NO_AAT_SHAPE
+  /* Mac OS X prefers morx over GSUB.  It also ships with various Indic fonts,
+   * all by 'MUTF' foundry (Tamil MN, Tamil Sangam MN, etc.), that have broken
+   * GSUB/GPOS tables.  Some have GSUB with zero scripts, those are ignored by
+   * our morx/GSUB preference code.  But if GSUB has non-zero scripts, we tend
+   * to prefer it over morx because we want to be consistent with other OpenType
+   * shapers.
+   *
+   * To work around broken Indic Mac system fonts, we ignore GSUB table if
+   * OS/2 VendorId is 'MUTF' and font has morx table as well.
+   *
+   * https://github.com/harfbuzz/harfbuzz/issues/1410
+   * https://github.com/harfbuzz/harfbuzz/issues/1348
+   * https://github.com/harfbuzz/harfbuzz/issues/1391
+   */
+  if (unlikely (face->table.OS2->achVendID == HB_TAG ('M','U','T','F') &&
+		face->table.morx->has_data ()))
+    return true;
+#endif
+
   return false;
 }
 
diff --git a/src/hb-ot-shape.cc b/src/hb-ot-shape.cc
index 8743387..1d12f1a 100644
--- a/src/hb-ot-shape.cc
+++ b/src/hb-ot-shape.cc
@@ -63,6 +63,23 @@
 			      const hb_feature_t             *user_features,
 			      unsigned int                    num_user_features);
 
+#ifndef HB_NO_AAT_SHAPE
+static inline bool
+_hb_apply_morx (hb_face_t *face)
+{
+  if (hb_options ().aat &&
+      hb_aat_layout_has_substitution (face))
+    return true;
+
+  /* Ignore empty GSUB tables. */
+  return (!hb_ot_layout_has_substitution (face) ||
+	  !hb_ot_layout_table_get_script_tags (face,
+					       HB_OT_TAG_GSUB,
+					       0, nullptr, nullptr)) &&
+	 hb_aat_layout_has_substitution (face);
+}
+#endif
+
 hb_ot_shape_planner_t::hb_ot_shape_planner_t (hb_face_t                     *face,
 					      const hb_segment_properties_t *props) :
 						face (face),
@@ -70,7 +87,7 @@
 						map (face, props),
 						aat_map (face, props)
 #ifndef HB_NO_AAT_SHAPE
-						, apply_morx (hb_aat_layout_has_substitution (face))
+						, apply_morx (_hb_apply_morx (face))
 #endif
 {
   shaper = hb_ot_shape_complex_categorize (this);
@@ -142,11 +159,15 @@
   if (0)
     ;
 #ifndef HB_NO_AAT_SHAPE
-  else if (hb_aat_layout_has_positioning (face))
+  else if (hb_options ().aat && hb_aat_layout_has_positioning (face))
     plan.apply_kerx = true;
 #endif
   else if (!apply_morx && !disable_gpos && hb_ot_layout_has_positioning (face))
     plan.apply_gpos = true;
+#ifndef HB_NO_AAT_SHAPE
+  else if (hb_aat_layout_has_positioning (face))
+    plan.apply_kerx = true;
+#endif
 
   if (!plan.apply_kerx && (!has_gpos_kern || !plan.apply_gpos))
   {