diff --git a/Library/Homebrew/cmd/audit.rb b/Library/Homebrew/cmd/audit.rb
index a49d01e06c..3f3e6f56cf 100644
--- a/Library/Homebrew/cmd/audit.rb
+++ b/Library/Homebrew/cmd/audit.rb
@@ -511,12 +511,14 @@ class FormulaAuditor
   end
 
   def audit_conditional_dep(dep, condition, line)
-    dep = Regexp.escape(dep)
+    quoted_dep = quote_dep(dep)
+    dep = Regexp.escape(dep.to_s)
+
     case condition
     when /if build\.include\? ['"]with-#{dep}['"]$/, /if build\.with\? ['"]#{dep}['"]$/
-      problem %{Replace #{line.inspect} with "depends_on #{quote_dep(dep)} => :optional"}
+      problem %{Replace #{line.inspect} with "depends_on #{quoted_dep} => :optional"}
     when /unless build\.include\? ['"]without-#{dep}['"]$/, /unless build\.without\? ['"]#{dep}['"]$/
-      problem %{Replace #{line.inspect} with "depends_on #{quote_dep(dep)} => :recommended"}
+      problem %{Replace #{line.inspect} with "depends_on #{quoted_dep} => :recommended"}
     end
   end