diff --git a/lib/ical_filter_proxy/filter_rule.rb b/lib/ical_filter_proxy/filter_rule.rb
index c464930..ea67381 100644
--- a/lib/ical_filter_proxy/filter_rule.rb
+++ b/lib/ical_filter_proxy/filter_rule.rb
@@ -13,6 +13,8 @@ def initialize(field, operator, values)
 
     def match_event?(filterable_event)
       event_data = filterable_event.send(field.to_sym)
+      return false if event_data.nil?  # Check if event_data is null
+    
       negation ^ evaluate(event_data, values)
     end