diff --git a/mo/util_format.py b/mo/util_format.py
index a4e7d70109883ea636e6f3c801ba094f424585e6..23ca852453bcff73402ed750c556d59c7e9323f2 100644
--- a/mo/util_format.py
+++ b/mo/util_format.py
@@ -116,7 +116,7 @@ def timedelta(d: datetime.datetime, ref: Optional[datetime.datetime] = None, des
     return f"{prefix}{value}{suffix}"
 
 
-def time_and_timedelta(d: datetime.datetime, ref: Optional[datetime.datetime] = None) -> str:
+def time_and_timedelta(d: Optional[datetime.datetime], ref: Optional[datetime.datetime] = None) -> str:
     if d is None:
         return '–'
     return f"{timeformat(d)} ({timedelta(d, ref)})"