diff --git a/packages/taler-util/src/wallet-types.ts b/packages/taler-util/src/wallet-types.ts
index 8737bc3f0..614610bb1 100644
--- a/packages/taler-util/src/wallet-types.ts
+++ b/packages/taler-util/src/wallet-types.ts
@@ -1643,8 +1643,8 @@ export const codecForPrepareDepositRequest = (): Codec<PrepareDepositRequest> =>
     .build("PrepareDepositRequest");
 
 export interface PrepareDepositResponse {
-  totalDepositCost: AmountJson;
-  effectiveDepositAmount: AmountJson;
+  totalDepositCost: AmountString;
+  effectiveDepositAmount: AmountString;
 }
 
 export const codecForCreateDepositGroupRequest =
diff --git a/packages/taler-wallet-core/src/operations/deposits.ts b/packages/taler-wallet-core/src/operations/deposits.ts
index 2b27d0f8f..4d617ee13 100644
--- a/packages/taler-wallet-core/src/operations/deposits.ts
+++ b/packages/taler-wallet-core/src/operations/deposits.ts
@@ -367,7 +367,10 @@ export async function prepareDepositGroup(
     payCoinSel,
   );
 
-  return { totalDepositCost, effectiveDepositAmount };
+  return {
+    totalDepositCost: Amounts.stringify(totalDepositCost),
+    effectiveDepositAmount: Amounts.stringify(effectiveDepositAmount),
+  };
 }
 export async function createDepositGroup(
   ws: InternalWalletState,