Adjust callers to match.
diff --git a/openstack/identity/v3/endpoints/requests_test.go b/openstack/identity/v3/endpoints/requests_test.go
index f988770..84cb2da 100644
--- a/openstack/identity/v3/endpoints/requests_test.go
+++ b/openstack/identity/v3/endpoints/requests_test.go
@@ -91,6 +91,7 @@
 		testhelper.TestMethod(t, r, "GET")
 		testhelper.TestHeader(t, r, "X-Auth-Token", tokenID)
 
+		w.Header().Add("Content-Type", "application/json")
 		fmt.Fprintf(w, `
 			{
 				"endpoints": [