diff --git a/Library/Homebrew/test/cleanup_spec.rb b/Library/Homebrew/test/cleanup_spec.rb
index 98cdb9bd07..b1bf3fb18d 100644
--- a/Library/Homebrew/test/cleanup_spec.rb
+++ b/Library/Homebrew/test/cleanup_spec.rb
@@ -64,8 +64,8 @@ describe Homebrew::Cleanup do
   end
 
   specify "::disk_cleanup_size" do
-    described_class.instance_eval("@disk_cleanup_size = 0")
-    expect(described_class.disk_cleanup_size).to eq(described_class.instance_variable_get("@disk_cleanup_size"))
+    disk_cleanup_size = described_class.instance_variable_get(:@disk_cleanup_size)
+    expect(described_class.disk_cleanup_size).to eq(disk_cleanup_size)
   end
 
   specify "::cleanup_formula" do