diff --git a/argocd/apps/mastodon.yaml b/argocd/apps/mastodon.yaml
index 34e9214..e0f5ff9 100644
--- a/argocd/apps/mastodon.yaml
+++ b/argocd/apps/mastodon.yaml
@@ -90,6 +90,7 @@ spec:
               clientSecret: o9GCnfhbw1jFaTPwJ4vm
               redirectUri: https://mastodon.t0rt1k.tech/auth/auth/openid_connect/callback
               assumeEmailIsVerified: false
+              clientAuthMethod: "client_secret_post"
             oauthGlobal:
               omniauthOnly: true