diff --git a/src/lhisp-oauth-client.t.ts b/src/lhisp-oauth-client.t.ts
index 460f6a1..d945320 100644
--- a/src/lhisp-oauth-client.t.ts
+++ b/src/lhisp-oauth-client.t.ts
@@ -40,6 +40,6 @@ export enum ContentType {
 }
 
 export const defaultGrantType = 'client_credentials';
-export const defaultAuthContentType = ContentType.APPLICATION_JSON;
+export const defaultAuthContentType = ContentType.APPLICATION_X_WWW_FORM_URLENCODED;
 export const defaultAuthHeaderName = 'Authorization';
 export const defaultTokenHeaderName = 'Authorization';
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