diff --git a/acme/acme_test.go b/acme/acme_test.go
index db9718a..b46f70d 100644
--- a/acme/acme_test.go
+++ b/acme/acme_test.go
@@ -975,6 +975,7 @@
 
 func TestFetchCertCancel(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		<-r.Context().Done()
 		w.Header().Set("Retry-After", "0")
 		w.WriteHeader(http.StatusBadRequest)
 	}))