diff --git a/lib/hawat/blueprints/detectors/forms.py b/lib/hawat/blueprints/detectors/forms.py
index f70d744ce0aa5f7aebec20735ed1dc91414e8e05..72986dd2653baae393d093552e353074ad7fb2ed 100644
--- a/lib/hawat/blueprints/detectors/forms.py
+++ b/lib/hawat/blueprints/detectors/forms.py
@@ -69,8 +69,8 @@ class BaseDetectorForm(hawat.forms.BaseItemForm):
     )
     credibility = wtforms.FloatField(
         lazy_gettext('Credibility:'),
+        default=1.0,
         validators=[
-            wtforms.validators.Optional(),
             wtforms.validators.NumberRange(min=0, max=1)
         ]
     )