diff --git a/src/aleph/chains/common.py b/src/aleph/chains/common.py
index 5903f1ec5..f7dd5a48c 100644
--- a/src/aleph/chains/common.py
+++ b/src/aleph/chains/common.py
@@ -307,29 +307,26 @@ async def incoming(
             **updates.get("$set", {}),
         }
         should_commit = True
-        # await Message.collection.insert_one(message)
-
-        # since it's on-chain, we need to keep that content.
-        # if message['item_type'] == 'ipfs' and app['config'].ipfs.enabled.value:
-        #     LOGGER.debug("Pining hash %s" % hash)
-        # await pin_hash(hash)
 
     if should_commit:
         update_op = UpdateOne(filters, updates, upsert=True)
-        bulk_ops = [
-            DbBulkOperation(CappedMessage, update_op),
-            DbBulkOperation(Message, update_op),
-        ]
+        bulk_ops = [DbBulkOperation(Message, update_op)]
+
+        # Capped collections do not accept updates that increase the size, so
+        # we must ignore confirmations.
+        if existing is None:
+            bulk_ops.append(DbBulkOperation(CappedMessage, update_op))
+
         return IncomingStatus.MESSAGE_HANDLED, bulk_ops
 
     return IncomingStatus.MESSAGE_HANDLED, []
 
 
-async def process_one_message(message: Dict):
+async def process_one_message(message: Dict, *args, **kwargs):
     """
     Helper function to process a message on the spot.
     """
-    status, ops = await incoming(message)
+    status, ops = await incoming(message, *args, **kwargs)
     for op in ops:
         await op.collection.collection.bulk_write([op.operation])
 
@@ -419,4 +416,6 @@ async def incoming_chaindata(content: Dict, context: TxContext):
     Content can be inline of "offchain" through an ipfs hash.
     For now we only add it to the database, it will be processed later.
     """
-    await PendingTX.collection.insert_one({"content": content, "context": asdict(context)})
+    await PendingTX.collection.insert_one(
+        {"content": content, "context": asdict(context)}
+    )
diff --git a/tests/chains/test_confirmation.py b/tests/chains/test_confirmation.py
new file mode 100644
index 000000000..fec9fc6dc
--- /dev/null
+++ b/tests/chains/test_confirmation.py
@@ -0,0 +1,111 @@
+import json
+from typing import Dict
+
+import pytest
+
+from aleph.chains.common import process_one_message
+from aleph.model.messages import CappedMessage, Message
+
+
+MESSAGE = {
+    "chain": "ETH",
+    "sender": "0x971300C78A38e0F85E60A3b04ae3fA70b4276B64",
+    "type": "POST",
+    "channel": "TEST",
+    "item_type": "inline",
+    "size": 70,
+    "time": 1646123806,
+    "item_content": '{"body": "Top 10 cutest Kodiak bears that will definitely murder you"}',
+    "item_hash": "fd14aaae5693710fae42fc58049f80ba7abdbf0cce00eb73e585bc89907eaad8",
+    "signature": "0xccb6a4c7e2a709accf941463a93064a9f34ea1d03b17fe9d117c80fb0878ee0a2f284af4afb37de187a1116c0cec5b3a8da89b40d5281919dbeebdffc50c86c71c",
+}
+
+
+def remove_id_key(mongodb_object: Dict) -> Dict:
+    return {k: v for k, v in mongodb_object.items() if k != "_id"}
+
+
+@pytest.mark.asyncio
+async def test_confirm_message(test_db):
+    """
+    Tests the flow of confirmation for real-time messages.
+    1. We process the message unconfirmed, as if it came through the P2P
+       network
+    2. We process the message again, this time as it it was fetched from
+       on-chain data.
+
+    We then check that the message was correctly updated in the messages
+    collection. We also check the capped messages collection used for
+    the websockets.
+    """
+
+    item_hash = MESSAGE["item_hash"]
+    content = json.loads(MESSAGE["item_content"])
+
+    await process_one_message(MESSAGE)
+    message_in_db = await Message.collection.find_one({"item_hash": item_hash})
+
+    assert message_in_db is not None
+    assert message_in_db["content"]["body"] == content["body"]
+    assert not message_in_db["confirmed"]
+
+    capped_message_in_db = await CappedMessage.collection.find_one(
+        {"item_hash": item_hash}
+    )
+    assert capped_message_in_db is not None
+    assert remove_id_key(message_in_db) == remove_id_key(capped_message_in_db)
+
+    # Now, confirm the message
+    chain_name, tx_hash, height = "ETH", "123", 8000
+    await process_one_message(
+        MESSAGE, chain_name=chain_name, tx_hash=tx_hash, height=height
+    )
+
+    message_in_db = await Message.collection.find_one({"item_hash": item_hash})
+
+    assert message_in_db is not None
+    assert message_in_db["confirmed"]
+    assert {"chain": chain_name, "hash": tx_hash, "height": height} in message_in_db[
+        "confirmations"
+    ]
+
+    capped_message_after_confirmation = await CappedMessage.collection.find_one(
+        {"item_hash": item_hash}
+    )
+
+    assert capped_message_after_confirmation == capped_message_in_db
+    assert not capped_message_after_confirmation["confirmed"]
+    assert "confirmations" not in capped_message_after_confirmation
+
+
+@pytest.mark.asyncio
+async def test_process_confirmed_message(test_db):
+    """
+    Tests that a confirmed message coming directly from the on-chain integration flow
+    is processed correctly, and that we get one confirmed entry in messages and one
+    in capped messages.
+    """
+
+    item_hash = MESSAGE["item_hash"]
+
+    # Now, confirm the message
+    chain_name, tx_hash, height = "ETH", "123", 8000
+    await process_one_message(
+        MESSAGE, chain_name=chain_name, tx_hash=tx_hash, height=height
+    )
+
+    message_in_db = await Message.collection.find_one({"item_hash": item_hash})
+
+    assert message_in_db is not None
+    assert message_in_db["confirmed"]
+
+    expected_confirmations = [{"chain": chain_name, "hash": tx_hash, "height": height}]
+    assert message_in_db["confirmations"] == expected_confirmations
+
+    capped_message_in_db = await CappedMessage.collection.find_one(
+        {"item_hash": item_hash}
+    )
+
+    assert remove_id_key(message_in_db) == remove_id_key(capped_message_in_db)
+    assert capped_message_in_db["confirmed"]
+    assert capped_message_in_db["confirmations"] == expected_confirmations