diff --git a/Library/Homebrew/cmd/audit.rb b/Library/Homebrew/cmd/audit.rb
index 78242f78a1..a73a0bef51 100644
--- a/Library/Homebrew/cmd/audit.rb
+++ b/Library/Homebrew/cmd/audit.rb
@@ -426,7 +426,7 @@ class FormulaAuditor
     return unless @strict
 
     regex = %r{https?://github.com/([^/]+)/([^/]+)/?.*}
-    _, user, repo = *regex.match(formula.stable.url)
+    _, user, repo = *regex.match(formula.stable.url) if formula.stable
     _, user, repo = *regex.match(formula.homepage) unless user
     return if !user || !repo