diff --git a/slixmpp_omemo/__init__.py b/slixmpp_omemo/__init__.py
index 1f6d978..6521c3e 100644
--- a/slixmpp_omemo/__init__.py
+++ b/slixmpp_omemo/__init__.py
@@ -579,8 +579,10 @@ class XEP_0384(BasePlugin):
             # or if we hit the same set of errors.
             errors = []  # type: List[omemo.exceptions.OMEMOException]
 
-            if expect_problems is not None:
-                expect_problems = {jid.bare: did for (jid, did) in expect_problems.items()}
+            if expect_problems is None:
+                expect_problems = {}
+
+            expect_problems = {jid.bare: did for (jid, did) in expect_problems.items()}
 
             try:
                 encrypted = self._omemo.encryptMessage(