diff --git a/ChangeLog.md b/ChangeLog.md
index 3c9a8490379eb..b27be81e226fb 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -20,6 +20,7 @@ Current Trunk
  - Only MEMFS is included by default, others (NODEFS, IDBFS, WORKERFS, PROXYFS)
    must be linked in explicitly, using `-lnodefs.js`, `-lidbfs.js`',
    `-lworkerfs.js`, `-lproxyfs.js`. See #9645
+ - New function emscripten_has_asyncify()
 
 v1.39.0: 10/18/2019
 -------------------
diff --git a/site/source/docs/api_reference/emscripten.h.rst b/site/source/docs/api_reference/emscripten.h.rst
index 55c9a1cd792ed..b3e3efe984e60 100644
--- a/site/source/docs/api_reference/emscripten.h.rst
+++ b/site/source/docs/api_reference/emscripten.h.rst
@@ -992,6 +992,13 @@ Functions
   :returns: The value of the specified setting. Note that for values other than an integer, a string is returned (cast the ``int`` return value to a ``char*``).
   :rtype: int
 
+.. c:function:: int emscripten_has_asyncify()
+
+  Returns whether pseudo-synchronous functions can be used.
+
+  :rtype: int
+  :returns: 1 if program was compiled with ASYNCIFY=1 or EMTERPRETER_ASYNC=1, 0 otherwise.
+
 
 .. c:function:: void emscripten_debugger()
 
diff --git a/src/library.js b/src/library.js
index e278e9455c35f..236b604b4e8df 100644
--- a/src/library.js
+++ b/src/library.js
@@ -4258,6 +4258,10 @@ LibraryManager.library = {
     return cache[fullname] = allocate(intArrayFromString(ret + ''), 'i8', ALLOC_NORMAL);
   },
 
+  emscripten_has_asyncify: function() {
+    return {{{ ASYNCIFY || EMTERPRETIFY_ASYNC }}};
+  },
+
   emscripten_debugger: function() {
     debugger;
   },
diff --git a/system/include/emscripten/emscripten.h b/system/include/emscripten/emscripten.h
index 389810f81de6a..99a012df644ad 100644
--- a/system/include/emscripten/emscripten.h
+++ b/system/include/emscripten/emscripten.h
@@ -228,6 +228,7 @@ int emscripten_get_worker_queue_size(worker_handle worker);
 // misc.
 
 int emscripten_get_compiler_setting(const char *name);
+int emscripten_has_asyncify();
 
 void emscripten_debugger(void);
 
diff --git a/tests/other/metadce/hello_world_fastcomp_O3_MAIN_MODULE.sent b/tests/other/metadce/hello_world_fastcomp_O3_MAIN_MODULE.sent
index 45dd728cea071..4807ca43c3916 100644
--- a/tests/other/metadce/hello_world_fastcomp_O3_MAIN_MODULE.sent
+++ b/tests/other/metadce/hello_world_fastcomp_O3_MAIN_MODULE.sent
@@ -887,6 +887,7 @@ _emscripten_gluOrtho2D
 _emscripten_gluPerspective
 _emscripten_gluProject
 _emscripten_gluUnProject
+_emscripten_has_asyncify
 _emscripten_hide_mouse
 _emscripten_html5_remove_all_event_listeners
 _emscripten_idb_async_delete
diff --git a/tests/test_core.py b/tests/test_core.py
index f79efeebada3e..e9b2ca1821c85 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1758,6 +1758,22 @@ def test_emscripten_get_compiler_setting(self):
     self.set_setting('RETAIN_COMPILER_SETTINGS', 1)
     self.do_run(open(src).read(), open(output).read().replace('waka', shared.EMSCRIPTEN_VERSION))
 
+  @no_fastcomp('ASYNCIFY has been removed from fastcomp')
+  def test_emscripten_has_asyncify(self):
+    src = r'''
+      #include <stdio.h>
+      #include <emscripten.h>
+
+      int main() {
+        printf("%d\n", emscripten_has_asyncify());
+        return 0;
+      }
+    '''
+    self.set_setting('ASYNCIFY', 0)
+    self.do_run(src, '0')
+    self.set_setting('ASYNCIFY', 1)
+    self.do_run(src, '1')
+
   # TODO: test only worked in non-fastcomp
   def test_inlinejs(self):
     self.skipTest('non-fastcomp is deprecated and fails in 3.5') # only supports EM_ASM
diff --git a/tests/test_other.py b/tests/test_other.py
index e625880b09fc7..91a9593e58329 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -8113,7 +8113,7 @@ def test_metadce_hello(self, *args):
                       4, [],        [],           8,   0,    0,  0), # noqa; totally empty!
     # we don't metadce with linkable code! other modules may want stuff
     # don't compare the # of functions in a main module, which changes a lot
-    'main_module_1': (['-O3', '-s', 'MAIN_MODULE=1'], 1600, [], [], 226403, None, 107, None), # noqa
+    'main_module_1': (['-O3', '-s', 'MAIN_MODULE=1'], 1601, [], [], 226403, None, 107, None), # noqa
     'main_module_2': (['-O3', '-s', 'MAIN_MODULE=2'],   13, [], [],  10017,   13,   9,   20), # noqa
   })
   @no_wasm_backend()