diff --git a/src/paveit/datamodels/norm_documents.py b/src/paveit/datamodels/norm_documents.py
index 1ffbf8e..d1e8938 100644
--- a/src/paveit/datamodels/norm_documents.py
+++ b/src/paveit/datamodels/norm_documents.py
@@ -21,7 +21,7 @@ class NormDocument(Document):
     number = StringField(required=True)    
     
     year =IntField(min_value=1900, max_value=2099)
-    month = IntField(min_value=1, max_value=12)
+    month = IntField(min_value=1, max_value=12, required=False) 
     
     meta = {
         'allow_inheritance': True,