diff --git a/neutron/plugins/ml2/plugin.py b/neutron/plugins/ml2/plugin.py
index 1dfc44b8780..2935e1b32c6 100644
--- a/neutron/plugins/ml2/plugin.py
+++ b/neutron/plugins/ml2/plugin.py
@@ -313,10 +313,10 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
         if not self.mechanism_manager.ordered_mech_drivers:
             return aliases
 
-        supported_extensions = set([])
+        supported_extensions = set(aliases)
         for mech_driver in self.mechanism_manager.ordered_mech_drivers:
-            supported_extensions |= mech_driver.obj.supported_extensions(
-                set(aliases))
+            supported_extensions &= mech_driver.obj.supported_extensions(
+                supported_extensions)
         return list(supported_extensions)
 
     @registry.receives(resources.PORT,
diff --git a/neutron/tests/unit/plugins/ml2/test_plugin.py b/neutron/tests/unit/plugins/ml2/test_plugin.py
index 67139410027..9ab6543d066 100644
--- a/neutron/tests/unit/plugins/ml2/test_plugin.py
+++ b/neutron/tests/unit/plugins/ml2/test_plugin.py
@@ -177,15 +177,14 @@ class TestMl2FilterExtensions(Ml2PluginV2TestCase):
     def test__filter_extensions_by_mech_driver(self):
         extension_aliases = ['ext1', 'ext2', 'ext3', 'ext4', 'ext5']
         supported_aliases = [{'ext0', 'ext1', 'ext2'},
-                             {'ext4', 'ext5', 'ext6'}]
+                             {'ext1', 'ext5', 'ext6'}]
         for idx, mech_driver in enumerate(
                 self.plugin.mechanism_manager.ordered_mech_drivers):
             mech_driver.obj._supported_extensions = supported_aliases[idx]
 
         supported_extensions = sorted(
             self.plugin._filter_extensions_by_mech_driver(extension_aliases))
-        self.assertEqual(['ext1', 'ext2', 'ext4', 'ext5'],
-                         supported_extensions)
+        self.assertEqual(['ext1'], supported_extensions)
 
 
 class TestMl2BasicGet(test_plugin.TestBasicGet,
diff --git a/releasenotes/notes/change-the-way-how-api-extensions-are-filtered-out-b4449e690cb64480.yaml b/releasenotes/notes/change-the-way-how-api-extensions-are-filtered-out-b4449e690cb64480.yaml
new file mode 100644
index 00000000000..7d2181bfea2
--- /dev/null
+++ b/releasenotes/notes/change-the-way-how-api-extensions-are-filtered-out-b4449e690cb64480.yaml
@@ -0,0 +1,13 @@
+---
+upgrade:
+  - |
+    The way the ML2 plugin filters out API extensions which are not supported
+    by loaded mechanism drivers has changed.
+    Before, the API extension was on the list if at least one of the mechanism drivers
+    supported it, but now the extension needs to be supported by all the mechanism
+    drivers. If at least one of them filters it out, it will be removed from
+    the final list of enabled API extensions.
+    Currently, only the OVN mechanism driver is filtering out some of the ML2
+    API extensions, thus if that mechanism driver is loaded in Neutron with any other
+    mechanism driver, the list of the enabled API extensions may be smaller than it
+    was before.