diff --git a/packages/web-util/src/utils/request.ts b/packages/web-util/src/utils/request.ts
index 8ce21b0e1..ef4d8e847 100644
--- a/packages/web-util/src/utils/request.ts
+++ b/packages/web-util/src/utils/request.ts
@@ -48,7 +48,7 @@ export async function defaultRequestHandler<T>(
     )}`;
   }
   requestHeaders["Content-Type"] =
-    options.contentType === "json" ? "application/json" : "text/plain";
+    !options.contentType || options.contentType === "json" ? "application/json" : "text/plain";
 
   if (options.talerAmlOfficerSignature) {
     requestHeaders["Taler-AML-Officer-Signature"] =