diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index fde273e..59abdf7 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -3658,24 +3658,33 @@
                                 const hb_set_t *feature_indices,
                                 hb_map_t *duplicate_feature_map /* OUT */) const
   {
-    hb_set_t unique_features;
-    hb_tag_t prev_t = get_feature_tag (feature_indices->get_min ());
+    if (feature_indices->is_empty ()) return;
+    hb_hashmap_t<hb_tag_t, hb_set_t *, (unsigned)-1, nullptr> unique_features;
     //find out duplicate features after subset
     for (unsigned i : feature_indices->iter ())
     {
       hb_tag_t t = get_feature_tag (i);
-      if (t != prev_t)
+      if (!unique_features.has (t))
       {
-        prev_t = t;
-        unique_features.clear ();
-        unique_features.add (i);
+        hb_set_t* indices = hb_set_create ();
+        if (unlikely (indices == hb_set_get_empty () ||
+                      !unique_features.set (t, indices)))
+        {
+          hb_set_destroy (indices);
+          for (auto _ : unique_features.iter ())
+            hb_set_destroy (_.second);
+          return;
+        }
+        if (unique_features.get (t))
+          unique_features.get (t)->add (i);
         duplicate_feature_map->set (i, i);
         continue;
       }
 
       bool found = false;
 
-      for (unsigned other_f_index : unique_features.iter ())
+      hb_set_t* same_tag_features = unique_features.get (t);
+      for (unsigned other_f_index : same_tag_features->iter ())
       {
         const Feature& f = get_feature (i);
         const Feature& other_f = get_feature (other_f_index);
@@ -3707,10 +3716,13 @@
       
       if (found == false)
       {
-        unique_features.add (i);
+        same_tag_features->add (i);
         duplicate_feature_map->set (i, i);
       }
     }
+
+    for (auto _ : unique_features.iter ())
+      hb_set_destroy (_.second);
   }
 
   void prune_features (const hb_map_t *lookup_indices, /* IN */
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index d02a3c0..1e446c6 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1013,24 +1013,15 @@
     }
 
     has_feature_filter = true;
+    hb_set_t features_set;
     for (; *features; features++)
+      features_set.add (*features);
+    
+    for (unsigned i = 0; i < g.get_feature_count (); i++)
     {
-      hb_tag_t tag = *features;
-      unsigned index;
-      g.find_feature_index (tag, &index);
-      if (index == OT::Index::NOT_FOUND_INDEX) continue;
-
-      feature_indices_filter.add(index);
-      for (int i = (int) index - 1; i >= 0; i--)
-      {
-        if (g.get_feature_tag (i) != tag) break;
+      hb_tag_t tag = g.get_feature_tag (i);
+      if (features_set.has (tag))
         feature_indices_filter.add(i);
-      }
-      for (unsigned i = index + 1; i < g.get_feature_count (); i++)
-      {
-        if (g.get_feature_tag (i) != tag) break;
-        feature_indices_filter.add(i);
-      }
     }
   }
 
diff --git a/test/subset/data/Makefile.am b/test/subset/data/Makefile.am
index f530fad..33ffb9e 100644
--- a/test/subset/data/Makefile.am
+++ b/test/subset/data/Makefile.am
@@ -36,6 +36,7 @@
 	expected/layout.notonastaliqurdu \
 	expected/layout.tinos \
 	expected/layout.duplicate_features \
+	expected/layout.unsorted_featurelist \
 	expected/cmap \
 	expected/cmap14 \
 	expected/sbix \
diff --git a/test/subset/data/Makefile.sources b/test/subset/data/Makefile.sources
index 2ed1056..34f2f07 100644
--- a/test/subset/data/Makefile.sources
+++ b/test/subset/data/Makefile.sources
@@ -34,6 +34,7 @@
 	tests/layout.tests \
 	tests/layout.tinos.tests \
 	tests/layout.duplicate_features.tests \
+	tests/layout.unsorted_featurelist.tests \
 	tests/sbix.tests \
 	tests/variable.tests \
 	tests/glyph_names.tests \
diff --git a/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.default.392,3a7,3b2,3c7.ttf b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.default.392,3a7,3b2,3c7.ttf
new file mode 100644
index 0000000..3fb42c6
--- /dev/null
+++ b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.default.392,3a7,3b2,3c7.ttf
Binary files differ
diff --git a/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.default.retain-all-codepoint.ttf b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.default.retain-all-codepoint.ttf
new file mode 100644
index 0000000..decba00
--- /dev/null
+++ b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.default.retain-all-codepoint.ttf
Binary files differ
diff --git a/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.layout-test.392,3a7,3b2,3c7.ttf b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.layout-test.392,3a7,3b2,3c7.ttf
new file mode 100644
index 0000000..a0b6145
--- /dev/null
+++ b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.layout-test.392,3a7,3b2,3c7.ttf
Binary files differ
diff --git a/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.layout-test.retain-all-codepoint.ttf b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.layout-test.retain-all-codepoint.ttf
new file mode 100644
index 0000000..2d76b5a
--- /dev/null
+++ b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.layout-test.retain-all-codepoint.ttf
Binary files differ
diff --git a/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.retain-gids.392,3a7,3b2,3c7.ttf b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.retain-gids.392,3a7,3b2,3c7.ttf
new file mode 100644
index 0000000..012bb16
--- /dev/null
+++ b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.retain-gids.392,3a7,3b2,3c7.ttf
Binary files differ
diff --git a/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.retain-gids.retain-all-codepoint.ttf b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.retain-gids.retain-all-codepoint.ttf
new file mode 100644
index 0000000..7ddb09a
--- /dev/null
+++ b/test/subset/data/expected/layout.unsorted_featurelist/NotoIKEAHebrewLatin-Regular.retain-gids.retain-all-codepoint.ttf
Binary files differ
diff --git a/test/subset/data/fonts/NotoIKEAHebrewLatin-Regular.ttf b/test/subset/data/fonts/NotoIKEAHebrewLatin-Regular.ttf
new file mode 100644
index 0000000..7566808
--- /dev/null
+++ b/test/subset/data/fonts/NotoIKEAHebrewLatin-Regular.ttf
Binary files differ
diff --git a/test/subset/data/tests/layout.unsorted_featurelist.tests b/test/subset/data/tests/layout.unsorted_featurelist.tests
new file mode 100644
index 0000000..9c77a7a
--- /dev/null
+++ b/test/subset/data/tests/layout.unsorted_featurelist.tests
@@ -0,0 +1,11 @@
+FONTS:
+NotoIKEAHebrewLatin-Regular.ttf
+
+PROFILES:
+layout-test.txt
+default.txt
+retain-gids.txt
+
+SUBSETS:
+U+392,U+3a7,U+3b2,U+3c7
+*
diff --git a/test/subset/meson.build b/test/subset/meson.build
index 9a5377c..a287136 100644
--- a/test/subset/meson.build
+++ b/test/subset/meson.build
@@ -28,6 +28,7 @@
   'layout.notonastaliqurdu',
   'layout.tinos',
   'layout.duplicate_features',
+  'layout.unsorted_featurelist',
   'cmap',
   'cmap14',
   'sbix',