diff --git a/test/threads/Makefile.am b/test/threads/Makefile.am
index c6879d776..f0347d492 100644
--- a/test/threads/Makefile.am
+++ b/test/threads/Makefile.am
@@ -7,6 +7,7 @@ SUBDIRS =
 EXTRA_DIST += \
 	meson.build \
 	hb-shape-threads.cc \
+	hb-subset-threads.cc \
 	$(NULL)
 
 # Convenience targets:
diff --git a/test/threads/hb-subset-threads.cc b/test/threads/hb-subset-threads.cc
new file mode 100644
index 000000000..80bcd2b5c
--- /dev/null
+++ b/test/threads/hb-subset-threads.cc
@@ -0,0 +1,180 @@
+#include <cassert>
+#include <cstring>
+#include <thread>
+#include <condition_variable>
+#include <vector>
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "hb-subset.h"
+
+enum operation_t
+{
+  subset_codepoints,
+  subset_glyphs
+};
+
+#define SUBSET_FONT_BASE_PATH "test/subset/data/fonts/"
+
+struct test_input_t
+{
+  const char *font_path;
+  const unsigned max_subset_size;
+} default_tests[] =
+{
+  {SUBSET_FONT_BASE_PATH "Roboto-Regular.ttf", 4000},
+  {SUBSET_FONT_BASE_PATH "Amiri-Regular.ttf", 4000},
+  {SUBSET_FONT_BASE_PATH "NotoNastaliqUrdu-Regular.ttf", 1000},
+  {SUBSET_FONT_BASE_PATH "NotoSansDevanagari-Regular.ttf", 1000},
+  {SUBSET_FONT_BASE_PATH "Mplus1p-Regular.ttf", 10000},
+  {SUBSET_FONT_BASE_PATH "SourceHanSans-Regular_subset.otf", 10000},
+  {SUBSET_FONT_BASE_PATH "SourceSansPro-Regular.otf", 2000},
+};
+
+
+static test_input_t *tests = default_tests;
+static unsigned num_tests = sizeof (default_tests) / sizeof (default_tests[0]);
+
+
+// https://en.cppreference.com/w/cpp/thread/condition_variable/wait
+static std::condition_variable cv;
+static std::mutex cv_m;
+static bool ready = false;
+
+static unsigned num_repetitions = 1;
+static unsigned num_threads = 3;
+
+static void AddCodepoints(const hb_set_t* codepoints_in_font,
+                          unsigned subset_size,
+                          hb_subset_input_t* input)
+{
+  auto *unicodes = hb_subset_input_unicode_set (input);
+  hb_codepoint_t cp = HB_SET_VALUE_INVALID;
+  for (unsigned i = 0; i < subset_size; i++) {
+    if (!hb_set_next (codepoints_in_font, &cp)) return;
+    hb_set_add (unicodes, cp);
+  }
+}
+
+static void AddGlyphs(unsigned num_glyphs_in_font,
+               unsigned subset_size,
+               hb_subset_input_t* input)
+{
+  auto *glyphs = hb_subset_input_glyph_set (input);
+  for (unsigned i = 0; i < subset_size && i < num_glyphs_in_font; i++) {
+    hb_set_add (glyphs, i);
+  }
+}
+
+static void subset (operation_t operation,
+                    const test_input_t &test_input,
+                    hb_face_t *face)
+{
+  // Wait till all threads are ready.
+  {
+    std::unique_lock<std::mutex> lk (cv_m);
+    cv.wait(lk, [] {return ready;});
+  }
+
+  unsigned subset_size = test_input.max_subset_size;
+
+  hb_subset_input_t* input = hb_subset_input_create_or_fail ();
+  assert (input);
+
+  switch (operation)
+  {
+    case subset_codepoints:
+    {
+      hb_set_t* all_codepoints = hb_set_create ();
+      hb_face_collect_unicodes (face, all_codepoints);
+      AddCodepoints(all_codepoints, subset_size, input);
+      hb_set_destroy (all_codepoints);
+    }
+    break;
+
+    case subset_glyphs:
+    {
+      unsigned num_glyphs = hb_face_get_glyph_count (face);
+      AddGlyphs(num_glyphs, subset_size, input);
+    }
+    break;
+  }
+
+  for (unsigned i = 0; i < num_repetitions; i++)
+  {
+    hb_face_t* subset = hb_subset_or_fail (face, input);
+    assert (subset);
+    hb_face_destroy (subset);
+  }
+
+  hb_subset_input_destroy (input);
+}
+
+static void test_operation (operation_t operation,
+                            const char *operation_name,
+                            const test_input_t &test_input)
+{
+  char name[1024] = "subset";
+  const char *p;
+  strcat (name, "/");
+  p = strrchr (test_input.font_path, '/');
+  strcat (name, p ? p + 1 : test_input.font_path);
+  strcat (name, "/");
+  strcat (name, operation_name);
+
+  printf ("Testing %s\n", name);
+
+  hb_face_t *face;
+  {
+    hb_blob_t *blob = hb_blob_create_from_file_or_fail (test_input.font_path);
+    assert (blob);
+    face = hb_face_create (blob, 0);
+    hb_blob_destroy (blob);
+  }
+
+  std::vector<std::thread> threads;
+  for (unsigned i = 0; i < num_threads; i++)
+    threads.push_back (std::thread (subset, operation, test_input, face));
+
+  {
+    std::unique_lock<std::mutex> lk (cv_m);
+    ready = true;
+  }
+  cv.notify_all();
+
+  for (unsigned i = 0; i < num_threads; i++)
+    threads[i].join ();
+
+  hb_face_destroy (face);
+}
+
+int main(int argc, char** argv)
+{
+  if (argc > 1)
+    num_threads = atoi (argv[1]);
+  if (argc > 2)
+    num_repetitions = atoi (argv[2]);
+
+  if (argc > 4)
+  {
+    num_tests = (argc - 3) / 2;
+    tests = (test_input_t *) calloc (num_tests, sizeof (test_input_t));
+    for (unsigned i = 0; i < num_tests; i++)
+    {
+      tests[i].font_path = argv[3 + i];
+    }
+  }
+
+  printf ("Num threads %u; num repetitions %u\n", num_threads, num_repetitions);
+  for (unsigned i = 0; i < num_tests; i++)
+  {
+    auto& test_input = tests[i];
+    test_operation (subset_codepoints, "codepoints", test_input);
+    test_operation (subset_glyphs, "glyphs", test_input);
+  }
+
+  if (tests != default_tests)
+    free (tests);
+}
diff --git a/test/threads/meson.build b/test/threads/meson.build
index 4402f4897..1848a1c6e 100644
--- a/test/threads/meson.build
+++ b/test/threads/meson.build
@@ -11,3 +11,18 @@ test('shape_threads', executable('hb-shape-threads', 'hb-shape-threads.cc',
   timeout: 300,
   suite: ['threads', 'slow'],
 )
+
+
+test('subset_threads', executable('hb-subset-threads', 'hb-subset-threads.cc',
+  dependencies: [
+    thread_dep
+  ],
+  cpp_args: [],
+  include_directories: [incconfig, incsrc],
+  link_with: [libharfbuzz, libharfbuzz_subset],
+  install: false,
+  ),
+  workdir: meson.current_source_dir() / '..' / '..',
+  timeout: 300,
+  suite: ['threads', 'slow'],
+)