diff --git a/test/unit-test/metric-middleware-test.js b/test/unit-test/metric-middleware-test.js
index acd9551..9103a2f 100644
--- a/test/unit-test/metric-middleware-test.js
+++ b/test/unit-test/metric-middleware-test.js
@@ -678,10 +678,11 @@ describe('metrics-middleware', () => {
             expect(Prometheus.register.getSingleMetric('http_request_size_bytes').labelNames).to.have.members(['method']);
         });
         it('and it\'s other type', () => {
-            middleware({
-                excludeDefaultMetricLabels: 'invalid'
-            });
-            expect(Prometheus.register.getSingleMetric('http_request_size_bytes').labelNames).to.have.members(['method', 'route', 'code']);
+            expect(() => {
+                middleware({
+                    excludeDefaultMetricLabels: 'invalid',
+                });
+            }).to.throw('excludeDefaultMetricLabels should be an array or a boolean');
         });
         afterEach(() => {
             Prometheus.register.clear();