diff --git a/openquake/engine/job/validation.py b/openquake/engine/job/validation.py
index <HASH>..<HASH> 100644
--- a/openquake/engine/job/validation.py
+++ b/openquake/engine/job/validation.py
@@ -1209,3 +1209,8 @@ def uniform_hazard_spectra_is_valid(mdl):
     if mdl.uniform_hazard_spectra and mdl.poes is None:
         return False, ['`poes` are required to compute UHS']
     return True, []
+
+
+def time_event_is_valid(_mdl):
+    # Any string is allowed, or `None`.
+    return True, []
job/validation:

Added missing `time_event_is_valid` function.