diff --git a/osc/commandline.py b/osc/commandline.py
index 521b097a..c2a7cbf9 100644
--- a/osc/commandline.py
+++ b/osc/commandline.py
@@ -2773,7 +2773,7 @@ Please submit there instead, or use --nodevelproject to force direct submission.
                         roles = ["creator"] if opts.mine else None
                         results = get_request_collection(
                             apiurl, project=project, package=package, user=who,
-                            states=state_list, types=opts.type, roles=roles)
+                            states=state_list, types=[opts.type], roles=roles)
 
             # Check if project actually exists if result list is empty
             if not results:
diff --git a/osc/core.py b/osc/core.py
index 9c7c95d5..d223caa7 100644
--- a/osc/core.py
+++ b/osc/core.py
@@ -4628,7 +4628,7 @@ def get_request_collection(
     package=None,
     states=None,
     review_states=None,
-    types=None,
+    types: List[str] = None,
     ids=None,
     withfullhistory=False
 ):
@@ -4667,6 +4667,7 @@ def get_request_collection(
             query["review_states"] = ",".join(review_states)
 
     if types:
+        assert not isinstance(types, str)
         query["types"] = ",".join(types)
 
     if ids: