diff --git a/doc/lightning-fetchinvoice.7.md b/doc/lightning-fetchinvoice.7.md
index 799bde5f6..a0d5235e9 100644
--- a/doc/lightning-fetchinvoice.7.md
+++ b/doc/lightning-fetchinvoice.7.md
@@ -56,7 +56,7 @@ On success, an object is returned, containing:
   - **description** (string, optional): a completely replaced *description* field
   - **vendor_removed** (string, optional): The *vendor* from the offer, which is missing in the invoice
   - **vendor** (string, optional): a completely replaced *vendor* field
-  - **msat** (msat, optional): the amount, if different from the offer amount multiplied by any *quantity* (or the offer had no amount, or was not in BTC).
+  - **amount_msat** (msat, optional): the amount, if different from the offer amount multiplied by any *quantity* (or the offer had no amount, or was not in BTC).
 - **next_period** (object, optional): Only for recurring invoices if the next period is under the *recurrence_limit*:
   - **counter** (u64): the index of the next period to fetchinvoice
   - **starttime** (u64): UNIX timestamp that the next period starts
@@ -88,4 +88,4 @@ RESOURCES
 
 Main web site: <https://github.com/ElementsProject/lightning>
 
-[comment]: # ( SHA256STAMP:e0033e40d86355e51abb48472f802a9a713ed5b2725828467515f9541207dac5)
+[comment]: # ( SHA256STAMP:fa4e9733716ba263e8288613633ec7e0e466c13fc8067b11588bfd3c88901672)
diff --git a/doc/schemas/fetchinvoice.schema.json b/doc/schemas/fetchinvoice.schema.json
index 951dcd19d..8c6d23655 100644
--- a/doc/schemas/fetchinvoice.schema.json
+++ b/doc/schemas/fetchinvoice.schema.json
@@ -33,7 +33,7 @@
           "type": "string",
           "description": "a completely replaced *vendor* field"
         },
-        "msat": {
+        "amount_msat": {
           "type": "msat",
           "description": "the amount, if different from the offer amount multiplied by any *quantity* (or the offer had no amount, or was not in BTC)."
         }
diff --git a/plugins/fetchinvoice.c b/plugins/fetchinvoice.c
index cca83e0c2..088affb61 100644
--- a/plugins/fetchinvoice.c
+++ b/plugins/fetchinvoice.c
@@ -345,9 +345,13 @@ static struct command_result *handle_invreq_response(struct command *cmd,
 	 */
 	/* We always tell them this unless it's trivial to calc and
 	 * exactly as expected. */
-	if (!expected_amount || *inv->amount != *expected_amount)
-		json_add_amount_msat_only(out, "msat",
+	if (!expected_amount || *inv->amount != *expected_amount) {
+		if (deprecated_apis)
+			json_add_amount_msat_only(out, "msat",
+						  amount_msat(*inv->amount));
+		json_add_amount_msat_only(out, "amount_msat",
 					  amount_msat(*inv->amount));
+	}
 	json_object_end(out);
 
 	/* We tell them about next period at this point, if any. */
diff --git a/tests/test_pay.py b/tests/test_pay.py
index 67704fe59..cb1e068b0 100644
--- a/tests/test_pay.py
+++ b/tests/test_pay.py
@@ -4708,7 +4708,7 @@ def test_fetchinvoice(node_factory, bitcoind):
                                      'description': 'USD test'})['bolt12']
 
     inv = l1.rpc.call('fetchinvoice', {'offer': offerusd})
-    assert inv['changes']['msat'] == Millisatoshi(int(10.05 * 5000))
+    assert inv['changes']['amount_msat'] == Millisatoshi(int(10.05 * 5000))
 
     # If we remove plugin, it can no longer give us an invoice.
     l3.rpc.plugin_stop(plugin)