diff --git a/src/library_syscall.js b/src/library_syscall.js
index f10461ed4..a193767d7 100644
--- a/src/library_syscall.js
+++ b/src/library_syscall.js
@@ -1003,7 +1003,7 @@ mergeInto(LibraryManager.library, {
           }
           return 0;
         }
-        default: abort('bad syscall ' + which);
+        default: abort('unimplemented syscall (' + which + ')');
       }
     } catch (e) {
       if (typeof FS === 'undefined' || !(e instanceof FS.ErrnoError)) abort(e);
diff --git a/tests/test_other.py b/tests/test_other.py
index 7122b5bae..24be3601a 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -4857,3 +4857,57 @@ int main(int argc, char** argv) {
     out, err = Popen([PYTHON, FILE_PACKAGER, 'test.data', '--preload', 'temp.txt', '--no-closure'], stdout=PIPE, stderr=PIPE).communicate()
     assert BAD not in out, out[max(out.index(BAD)-80, 0) : min(out.index(BAD)+80, len(out)-1)]
 
+  def test_all_syscalls(self):
+    # find all syscalls
+    Popen([PYTHON, EMCC, path_from_root('tests', 'hello_world.c'), '-s', 'LINKABLE=1']).communicate()
+    gen = open('a.out.js').read()
+    assert 'function _printf' in gen, 'libc is included'
+    assert 'function _printf_core' in gen, 'musl libc is included'
+    assert 'function _strtoull_l' in gen, 'all parts of musl are included'
+    seen = set()
+    for syscall in ['___syscall', '___syscall_cp']:
+      calls = re.findall(syscall + '\(\d+,', gen)
+      assert len(calls) > 0
+      for call in calls:
+        num = call.split('(')[1][:-1]
+        num = int(num) # must be integers, no indirect syscalls are allowed
+        seen.add(num)
+    print seen, len(seen)
+    # generate code to test them for support
+    open('test.cpp', 'w').write(r'''
+#include <stdio.h>
+#include <emscripten.h>
+
+void test(int num) {
+  EM_ASM_({
+    var num = $0;
+    // we expect them to fail! we are not passing in valid parameters or anything. but the error tells us if they are missing or not
+    // suppress printErrs, and restore all of memory to remove all side effects (at least those not in JS)
+    Module.printErr = function(){};
+    var mem = new Uint8Array(HEAPU8);
+    abort = function(text) {
+      if (text.indexOf('unimplemented syscall') >= 0) Module.print('unimplemented syscall: ' + num);
+      throw 'continue';
+    };
+    try {
+      ___syscall(num);
+    } catch (e) {
+    }
+    HEAPU8.set(mem);
+  }, num);
+}
+
+int main() {
+  // expected syscalls
+  printf("these should work...\n");
+%s
+  // test a fake syscall, see the error
+  printf("this should fail...\n");
+  test(-1);
+  return 0;
+}
+''' % '\n'.join(['  test(%d);' % num for num in seen]))
+    Popen([PYTHON, EMCC, 'test.cpp', '-o', 'test.js']).communicate()
+    engine = SPIDERMONKEY_ENGINE if SPIDERMONKEY_ENGINE in JS_ENGINES else JS_ENGINES[0] # node is slow on this, sm is fast
+    self.assertContained('these should work...\nthis should fail...\nunimplemented syscall: -1\n', run_js('test.js', engine=engine))
+