diff --git a/Library/Homebrew/cask/config.rb b/Library/Homebrew/cask/config.rb
index 706ab32300..ae3533e7a8 100644
--- a/Library/Homebrew/cask/config.rb
+++ b/Library/Homebrew/cask/config.rb
@@ -194,12 +194,12 @@ module Cask
     end
 
     sig { params(options: T.untyped).returns(String) }
-    def to_json(**options)
+    def to_json(*options)
       {
         default:  default,
         env:      env,
         explicit: explicit,
-      }.to_json(**options)
+      }.to_json(*options)
     end
   end
 end