diff --git a/Library/Homebrew/dev-cmd/tap-new.rb b/Library/Homebrew/dev-cmd/tap-new.rb
index 6e136cb1dd..1471b16f58 100644
--- a/Library/Homebrew/dev-cmd/tap-new.rb
+++ b/Library/Homebrew/dev-cmd/tap-new.rb
@@ -95,8 +95,8 @@ module Homebrew
                   uses: actions/cache@v4
                   with:
                     path: ${{ steps.set-up-homebrew.outputs.gems-path }}
-                    key: ${{ runner.os }}-rubygems-${{ steps.set-up-homebrew.outputs.gems-hash }}
-                    restore-keys: ${{ runner.os }}-rubygems-
+                    key: ${{ matrix.os }}-rubygems-${{ steps.set-up-homebrew.outputs.gems-hash }}
+                    restore-keys: ${{ matrix.os }}-rubygems-
 
                 - run: brew test-bot --only-cleanup-before