diff --git a/atst/forms/validators.py b/atst/forms/validators.py
index b6606062..ff4b2366 100644
--- a/atst/forms/validators.py
+++ b/atst/forms/validators.py
@@ -32,7 +32,7 @@ def IsNumber(message=translate("forms.validators.is_number_message")):
     def _is_number(form, field):
         try:
             int(field.data)
-        except ValueError:
+        except (ValueError, TypeError):
             raise ValidationError(message)
 
     return _is_number
diff --git a/tests/forms/test_validators.py b/tests/forms/test_validators.py
index fe12cd58..2dc80659 100644
--- a/tests/forms/test_validators.py
+++ b/tests/forms/test_validators.py
@@ -17,7 +17,7 @@ class TestIsNumber:
         dummy_field.data = valid
         validator(dummy_form, dummy_field)
 
-    @pytest.mark.parametrize("invalid", ["12.1", "two", ""])
+    @pytest.mark.parametrize("invalid", ["12.1", "two", "", None])
     def test_IsNumber_rejects_anything_else(self, invalid, dummy_form, dummy_field):
         validator = IsNumber()
         dummy_field.data = invalid