diff --git a/cashu/core/base.py b/cashu/core/base.py
index d9f1dc0..4ae524e 100644
--- a/cashu/core/base.py
+++ b/cashu/core/base.py
@@ -530,7 +530,13 @@ class CheckFeesResponse_deprecated(BaseModel):
 
 class PostRestoreResponse(BaseModel):
     outputs: List[BlindedMessage] = []
-    promises: List[BlindedSignature] = []
+    signatures: List[BlindedSignature] = []
+    promises: Optional[List[BlindedSignature]] = []  # deprecated since 0.15.1
+
+    # duplicate value of "signatures" for backwards compatibility with old clients < 0.15.1
+    def __init__(self, **data):
+        super().__init__(**data)
+        self.promises = self.signatures
 
 
 # ------- KEYSETS -------
diff --git a/cashu/mint/router.py b/cashu/mint/router.py
index d0cac90..de3a07c 100644
--- a/cashu/mint/router.py
+++ b/cashu/mint/router.py
@@ -355,4 +355,4 @@ async def check_state(
 async def restore(payload: PostMintRequest) -> PostRestoreResponse:
     assert payload.outputs, Exception("no outputs provided.")
     outputs, promises = await ledger.restore(payload.outputs)
-    return PostRestoreResponse(outputs=outputs, promises=promises)
+    return PostRestoreResponse(outputs=outputs, signatures=promises)
diff --git a/cashu/mint/router_deprecated.py b/cashu/mint/router_deprecated.py
index a2ac71b..f2cb96c 100644
--- a/cashu/mint/router_deprecated.py
+++ b/cashu/mint/router_deprecated.py
@@ -360,4 +360,4 @@ async def check_spendable_deprecated(
 async def restore(payload: PostMintRequest_deprecated) -> PostRestoreResponse:
     assert payload.outputs, Exception("no outputs provided.")
     outputs, promises = await ledger.restore(payload.outputs)
-    return PostRestoreResponse(outputs=outputs, promises=promises)
+    return PostRestoreResponse(outputs=outputs, signatures=promises)
diff --git a/cashu/wallet/wallet.py b/cashu/wallet/wallet.py
index 9dd07b8..5473506 100644
--- a/cashu/wallet/wallet.py
+++ b/cashu/wallet/wallet.py
@@ -697,7 +697,14 @@ class LedgerAPI(LedgerAPIDeprecated, object):
         self.raise_on_error_request(resp)
         response_dict = resp.json()
         returnObj = PostRestoreResponse.parse_obj(response_dict)
-        return returnObj.outputs, returnObj.promises
+
+        # BEGIN backwards compatibility < 0.15.1
+        # if the mint returns promises, duplicate into signatures
+        if returnObj.promises:
+            returnObj.signatures = returnObj.promises
+        # END backwards compatibility < 0.15.1
+
+        return returnObj.outputs, returnObj.signatures
 
 
 class Wallet(LedgerAPI, WalletP2PK, WalletHTLC, WalletSecrets):
diff --git a/cashu/wallet/wallet_deprecated.py b/cashu/wallet/wallet_deprecated.py
index cca86fb..db5e927 100644
--- a/cashu/wallet/wallet_deprecated.py
+++ b/cashu/wallet/wallet_deprecated.py
@@ -408,7 +408,14 @@ class LedgerAPIDeprecated(SupportsHttpxClient, SupportsMintURL):
         self.raise_on_error(resp)
         response_dict = resp.json()
         returnObj = PostRestoreResponse.parse_obj(response_dict)
-        return returnObj.outputs, returnObj.promises
+
+        # BEGIN backwards compatibility < 0.15.1
+        # if the mint returns promises, duplicate into signatures
+        if returnObj.promises:
+            returnObj.signatures = returnObj.promises
+        # END backwards compatibility < 0.15.1
+
+        return returnObj.outputs, returnObj.signatures
 
     @async_set_httpx_client
     @async_ensure_mint_loaded_deprecated