diff --git a/packages/toolkit/src/query/fetchBaseQuery.ts b/packages/toolkit/src/query/fetchBaseQuery.ts
index 0814e3e2e2..460eeb47ab 100644
--- a/packages/toolkit/src/query/fetchBaseQuery.ts
+++ b/packages/toolkit/src/query/fetchBaseQuery.ts
@@ -218,7 +218,7 @@ export function fetchBaseQuery({
       config.headers.set('content-type', 'application/json')
     }
 
-    if (body && isJsonContentType(config.headers)) {
+    if (isJsonifiable(body) && isJsonContentType(config.headers)) {
       config.body = JSON.stringify(body)
     }