--- a/cubicweb/__init__.py	Mon Feb 06 15:43:19 2017 +0100
+++ b/cubicweb/__init__.py	Wed Feb 08 10:31:26 2017 +0100
@@ -307,6 +307,13 @@
                 return pkgutil.ImpLoader(fullname, *modinfo)
 
     def load_module(self, fullname):
+        try:
+            # If there is an existing module object named 'fullname' in
+            # sys.modules , the loader must use that existing module.
+            # Otherwise, the reload() builtin will not work correctly.
+            return sys.modules[fullname]
+        except KeyError:
+            pass
         if fullname != 'cubes':
             raise ImportError('No module named {0}'.format(fullname))
         mod = sys.modules[fullname] = types.ModuleType(fullname, doc='CubicWeb cubes')

--- a/cubicweb/test/unittest_cubes.py	Mon Feb 06 15:43:19 2017 +0100
+++ b/cubicweb/test/unittest_cubes.py	Wed Feb 08 10:31:26 2017 +0100
@@ -93,6 +93,17 @@
             from cubes.foo import bar
             self.assertEqual(bar.baz, 1)
 
+    def test_reload_cube(self):
+        """reloading cubes twice should return the same module"""
+        CubicWebConfiguration.cls_adjust_sys_path()
+        import cubes
+        if PY2:
+            new = reload(cubes)
+        else:
+            import importlib
+            new = importlib.reload(cubes)
+        self.assertIs(new, cubes)
+
     def test_import_legacy_cube(self):
         """Check that importing a legacy cube works when sys.path got adjusted.
         """