diff --git a/packages/backend/server/src/plugins/calendar/providers/def.ts b/packages/backend/server/src/plugins/calendar/providers/def.ts
index a9089d2ab6..02ad30482a 100644
--- a/packages/backend/server/src/plugins/calendar/providers/def.ts
+++ b/packages/backend/server/src/plugins/calendar/providers/def.ts
@@ -154,8 +154,8 @@ export abstract class CalendarProvider {
 
   protected async fetchJson<T>(url: string, init?: RequestInit) {
     const response = await fetch(url, {
-      headers: { Accept: 'application/json', ...init?.headers },
       ...init,
+      headers: { ...init?.headers, Accept: 'application/json' },
     });
     const body = await response.text();
     if (!response.ok) {
diff --git a/packages/backend/server/src/plugins/oauth/providers/def.ts b/packages/backend/server/src/plugins/oauth/providers/def.ts
index 8258e860d2..695eea7a07 100644
--- a/packages/backend/server/src/plugins/oauth/providers/def.ts
+++ b/packages/backend/server/src/plugins/oauth/providers/def.ts
@@ -84,8 +84,8 @@ export abstract class OAuthProvider {
     options?: { treatServerErrorAsInvalid?: boolean }
   ) {
     const response = await fetch(url, {
-      headers: { Accept: 'application/json', ...init?.headers },
       ...init,
+      headers: { ...init?.headers, Accept: 'application/json' },
     });
 
     const body = await response.text();