diff --git a/cgroup_exporter_test.go b/cgroup_exporter_test.go
index f07274c..3b8be88 100644
--- a/cgroup_exporter_test.go
+++ b/cgroup_exporter_test.go
@@ -68,7 +68,7 @@ func TestMetricsHandler(t *testing.T) {
 		t.Fatalf("Unexpected error GET /metrics: %s", err.Error())
 	}
 	if !strings.Contains(body, "cgroup_memory_used_bytes{cgroup=\"/user.slice/user-20821.slice\"} 8.081408e+06") {
-		t.Errorf("Unexpected value for cgroup_memory_used_bytes")
+		t.Errorf("Unexpected value for cgroup_memory_used_bytes: %s", body)
 	}
 }