diff --git a/app/models/conference.rb b/app/models/conference.rb
index 4416d656..ef7b0935 100644
--- a/app/models/conference.rb
+++ b/app/models/conference.rb
@@ -56,7 +56,7 @@ class Conference < ActiveRecord::Base
                         :end_date
 
   validates_uniqueness_of :short_title
-  validates_format_of :short_title, with: /\A[a-zA-Z0-9_-]*\z/
+  validates_format_of :short_title, with: /\A[a-z0-9_]*\z/
   validates :registration_limit, numericality: { only_integer: true, greater_than_or_equal_to: 0 }
 
   # This validation is needed since a conference with a start date greater than the end date is not possible