diff --git a/src/saml2/mdstore.py b/src/saml2/mdstore.py
index 621752b..438d916 100644
--- a/src/saml2/mdstore.py
+++ b/src/saml2/mdstore.py
@@ -992,10 +992,7 @@ class MetadataStore(MetaData):
             try:
                 srvs = _md[entity_id][typ]
             except KeyError:
-                return None
-
-            if not srvs:
-                return srvs
+                continue
 
             res = []
             for srv in srvs:
@@ -1005,6 +1002,8 @@ class MetadataStore(MetaData):
                             res.append(elem)
             return res
 
+        return None
+
     def ext_service(self, entity_id, typ, service, binding=None):
         known_entity = False
         for key, _md in self.metadata.items():
diff --git a/tests/test_30_mdstore.py b/tests/test_30_mdstore.py
index d4dd166..aadd772 100644
--- a/tests/test_30_mdstore.py
+++ b/tests/test_30_mdstore.py
@@ -2,6 +2,7 @@
 # -*- coding: utf-8 -*-
 import datetime
 import re
+from collections import OrderedDict
 
 from future.backports.urllib.parse import quote_plus
 
@@ -455,5 +456,16 @@ def test_metadata_extension_algsupport():
     mdf = mds.metadata[full_path("uu.xml")]
     assert mds
 
+
+def test_extension():
+    mds = MetadataStore(ATTRCONV, None)
+    # use ordered dict to force expected entity to be last
+    metadata = OrderedDict()
+    metadata["1"] = {"entity1": {}}
+    metadata["2"] = {"entity2": {"idpsso_descriptor": [{"extensions": {"extension_elements": [{"__class__": "test"}]}}]}}
+    mds.metadata = metadata
+    assert mds.extension("entity2", "idpsso_descriptor", "test")
+
+
 if __name__ == "__main__":
     test_metadata_extension_algsupport()