diff --git a/packages/ditto/controllers/api/cashu.ts b/packages/ditto/controllers/api/cashu.ts
index 18cbb7a5..d12fb01d 100644
--- a/packages/ditto/controllers/api/cashu.ts
+++ b/packages/ditto/controllers/api/cashu.ts
@@ -137,7 +137,7 @@ route.post('/mint/:quote_id', userMiddleware({ enc: 'nip44' }), async (c) => {
               pubkey,
               JSON.stringify([
                 ['direction', 'in'],
-                ['amount', amount],
+                ['amount', String(amount)],
                 ['e', unspentProofs.id, conf.relay, 'created'],
               ]),
             ),
diff --git a/packages/ditto/middleware/swapNutzapsMiddleware.ts b/packages/ditto/middleware/swapNutzapsMiddleware.ts
index b7551d0b..8dd1510d 100644
--- a/packages/ditto/middleware/swapNutzapsMiddleware.ts
+++ b/packages/ditto/middleware/swapNutzapsMiddleware.ts
@@ -79,7 +79,7 @@ export const swapNutzapsMiddleware: MiddlewareHandler = async (c, next) => {
           pubkey,
           JSON.stringify([
             ['direction', 'in'],
-            ['amount', amount],
+            ['amount', String(amount)],
             ['e', unspentProofs.id, conf.relay, 'created'],
           ]),
         ),