diff --git a/mslib/mscolab/models.py b/mslib/mscolab/models.py
index 938f7ede1..24121252c 100644
--- a/mslib/mscolab/models.py
+++ b/mslib/mscolab/models.py
@@ -213,5 +213,7 @@ def __init__(self, op_id, u_id, commit_hash, version_name=None, comment=None):
         self.op_id = int(op_id)
         self.u_id = int(u_id)
         self.commit_hash = str(commit_hash)
-        self.version_name = str(version_name)
-        self.comment = str(comment)
+        if version_name is not None:
+            self.version_name = str(version_name)
+        if comment is not None:
+            self.comment = str(comment)