diff --git a/tests/instance_test.rb b/tests/instance_test.rb
index bbd3776..0d3c99a 100644
--- a/tests/instance_test.rb
+++ b/tests/instance_test.rb
@@ -104,7 +104,7 @@ def test_call_string
   end
 
   def test_call_void
-    assert_equal nil, Wasmer::Instance.new(self.bytes).exports.void
+    assert_nil Wasmer::Instance.new(self.bytes).exports.void
   end
 
   def test_exports