diff --git a/async_substrate_interface/async_substrate.py b/async_substrate_interface/async_substrate.py
index f0c4a92..d7df725 100644
--- a/async_substrate_interface/async_substrate.py
+++ b/async_substrate_interface/async_substrate.py
@@ -2395,6 +2395,9 @@ async def _make_rpc_request(
     ) -> RequestResults:
         request_manager = RequestManager(payloads)
 
+        if len(set(x["id"] for x in payloads)) != len(payloads):
+            raise ValueError("Payloads must have unique ids")
+
         subscription_added = False
 
         async with self.ws as ws:
@@ -3670,6 +3673,7 @@ async def query_map(
                         self.decode_ss58,
                     )
             else:
+                # storage item and value scale type are not included here because this is batch-decoded in rust
                 page_batches = [
                     result_keys[i : i + page_size]
                     for i in range(0, len(result_keys), page_size)
diff --git a/async_substrate_interface/sync_substrate.py b/async_substrate_interface/sync_substrate.py
index 9d743c9..5349b31 100644
--- a/async_substrate_interface/sync_substrate.py
+++ b/async_substrate_interface/sync_substrate.py
@@ -1896,6 +1896,10 @@ def _make_rpc_request(
     ) -> RequestResults:
         request_manager = RequestManager(payloads)
         _received = {}
+
+        if len(set(x["id"] for x in payloads)) != len(payloads):
+            raise ValueError("Payloads must have unique ids")
+
         subscription_added = False
 
         ws = self.connect(init=False if attempt == 1 else True)