diff --git a/oauth2/handler.go b/oauth2/handler.go
index dd4e7f52f3b..5662be5cc8e 100644
--- a/oauth2/handler.go
+++ b/oauth2/handler.go
@@ -909,7 +909,7 @@ type oAuth2TokenExchange struct {
 	Scope string `json:"scope"`
 
 	// To retrieve a refresh token request the id_token scope.
-	IDToken int `json:"id_token"`
+	IDToken string `json:"id_token"`
 
 	// The access token issued by the authorization server.
 	AccessToken string `json:"access_token"`