diff --git a/api/http/handler/auth/authenticate.go b/api/http/handler/auth/authenticate.go
index a2f29e6f9..02159c275 100644
--- a/api/http/handler/auth/authenticate.go
+++ b/api/http/handler/auth/authenticate.go
@@ -52,7 +52,7 @@ func (handler *Handler) authenticate(w http.ResponseWriter, r *http.Request) *ht
 		return &httperror.HandlerError{http.StatusInternalServerError, "Unable to retrieve a user with the specified username from the database", err}
 	}
 
-	if err == portainer.ErrObjectNotFound && settings.AuthenticationMethod == portainer.AuthenticationInternal {
+	if err == portainer.ErrObjectNotFound && (settings.AuthenticationMethod == portainer.AuthenticationInternal || settings.AuthenticationMethod == portainer.AuthenticationOAuth) {
 		return &httperror.HandlerError{http.StatusUnprocessableEntity, "Invalid credentials", portainer.ErrUnauthorized}
 	}