diff --git a/Lib/test/test_importlib/test_api.py b/Lib/test/test_importlib/test_api.py
--- a/Lib/test/test_importlib/test_api.py
+++ b/Lib/test/test_importlib/test_api.py
@@ -410,6 +410,25 @@
                     self.assertEqual(loader.path, init_path)
                     self.assertEqual(ns, expected)
 
+    def test_reload_submodule(self):
+        # See #19851.
+        name = 'spam'
+        subname = 'ham'
+        submod = '{}.{}'.format(name, subname)
+        with support.temp_cwd(None) as cwd:
+            with util.uncache(name):
+                with support.DirsOnSysPath(cwd):
+                    init_path = os.path.join(cwd, name, '__init__.py')
+                    sub_path = os.path.join(cwd, name, subname + '.py')
+                    os.mkdir(name)
+                    with open(init_path, 'w'):
+                        pass
+                    with open(sub_path, 'w') as sub_file:
+                        sub_file.write('eggs = None')
+
+                    ham = self.init.import_module(submod)
+                    self.init.reload(ham)
+
 
 class Frozen_ReloadTests(ReloadTests, unittest.TestCase):
     init = frozen_init