diff --git a/service/oauth/oauth.go b/service/oauth/oauth.go
index 719c7339..d15bd94b 100644
--- a/service/oauth/oauth.go
+++ b/service/oauth/oauth.go
@@ -48,10 +48,10 @@ type (
 		ClientID            string `json:"client_id" binding:"required"`
 		ResponseType        string `json:"response_type" binding:"required,eq=code"`
 		RedirectURI         string `json:"redirect_uri" binding:"required"`
-		State               string `json:"state" binding:"max=255"`
+		State               string `json:"state" binding:"max=4096"`
 		Scope               string `json:"scope" binding:"required"`
 		CodeChallenge       string `json:"code_challenge" binding:"max=255"`
-		CodeChallengeMethod string `json:"code_challenge_method" binding:"eq=S256,omitempty"`
+		CodeChallengeMethod string `json:"code_challenge_method" binding:"omitempty,eq=S256"`
 	}
 )