diff --git a/Library/Homebrew/cache_store.rb b/Library/Homebrew/cache_store.rb
index 20cd304a7c..1bc48537e3 100644
--- a/Library/Homebrew/cache_store.rb
+++ b/Library/Homebrew/cache_store.rb
@@ -77,7 +77,7 @@ class CacheStoreDatabase
           args: [
             "-rdbm",
             "-e",
-            "DBM.open('#{dbm_file_path}', #{DATABASE_MODE}, DBM::READER).size",
+            "DBM.open('#{dbm_file_path}', #{DATABASE_MODE}, DBM::READER).values.size",
           ],
           print_stderr: false,
           must_succeed: true,