diff --git a/Library/Homebrew/rubocops/cask/homepage_url_trailing_slash.rb b/Library/Homebrew/rubocops/cask/homepage_url_trailing_slash.rb
index 1d97333267..68a2ea7e35 100644
--- a/Library/Homebrew/rubocops/cask/homepage_url_trailing_slash.rb
+++ b/Library/Homebrew/rubocops/cask/homepage_url_trailing_slash.rb
@@ -17,7 +17,7 @@ module RuboCop
           url_node = stanza.stanza_node.first_argument
           url = url_node.str_content
 
-          return unless url.match?(%r{^.+://[^/]+$})
+          return unless url&.match?(%r{^.+://[^/]+$})
 
           add_offense(url_node, location: :expression,
                                 message:  format(MSG_NO_SLASH, url: url))