diff --git a/doc/API.md b/doc/API.md
index 1764eded..f126fffb 100644
--- a/doc/API.md
+++ b/doc/API.md
@@ -109,3 +109,24 @@ This command will refuse to create any output worth less than 5k sats.
 | Field          | Type      | Description                                          |
 | -------------- | --------- | ---------------------------------------------------- |
 | `psbt`         | string    | PSBT of the spending transaction, encoded as base64. |
+
+
+### `updatespend`
+
+Store the PSBT of a Spend transaction in database, updating it if it already exists.
+
+Will merge the partial signatures for all inputs if a PSBT for a transaction with the same txid
+exists in DB.
+
+#### Request
+
+| Field     | Type   | Description                                 |
+| --------- | ------ | ------------------------------------------- |
+| `psbt`    | string | Base64-encoded PSBT of a Spend transaction. |
+
+#### Response
+
+This command does not return anything for now.
+
+| Field          | Type      | Description                                          |
+| -------------- | --------- | ---------------------------------------------------- |
diff --git a/src/jsonrpc/api.rs b/src/jsonrpc/api.rs
index 9f861edc..90f224c6 100644
--- a/src/jsonrpc/api.rs
+++ b/src/jsonrpc/api.rs
@@ -5,7 +5,7 @@ use crate::{
 
 use std::{collections::HashMap, convert::TryInto, str::FromStr};
 
-use miniscript::bitcoin;
+use miniscript::bitcoin::{self, consensus, util::psbt::PartiallySignedTransaction as Psbt};
 
 fn create_spend(control: &DaemonControl, params: Params) -> Result<serde_json::Value, Error> {
     let outpoints = params
@@ -47,6 +47,19 @@ fn create_spend(control: &DaemonControl, params: Params) -> Result<serde_json::V
     Ok(serde_json::json!(&res))
 }
 
+fn update_spend(control: &DaemonControl, params: Params) -> Result<serde_json::Value, Error> {
+    let psbt: Psbt = params
+        .get(0, "psbt")
+        .ok_or(Error::invalid_params("Missing 'psbt' parameter."))?
+        .as_str()
+        .and_then(|s| base64::decode(&s).ok())
+        .and_then(|bytes| consensus::deserialize(&bytes).ok())
+        .ok_or(Error::invalid_params("Invalid 'feerate' parameter."))?;
+    control.update_spend(psbt)?;
+
+    Ok(serde_json::json!({}))
+}
+
 /// Handle an incoming JSONRPC2 request.
 pub fn handle_request(control: &DaemonControl, req: Request) -> Result<Response, Error> {
     let result = match req.method.as_str() {
@@ -60,6 +73,12 @@ pub fn handle_request(control: &DaemonControl, req: Request) -> Result<Response,
         "getnewaddress" => serde_json::json!(&control.get_new_address()),
         "listcoins" => serde_json::json!(&control.list_coins()),
         "stop" => serde_json::json!({}),
+        "updatespend" => {
+            let params = req
+                .params
+                .ok_or(Error::invalid_params("Missing 'psbt' parameter."))?;
+            update_spend(control, params)?
+        }
         _ => {
             return Err(Error::method_not_found());
         }
diff --git a/tests/test_rpc.py b/tests/test_rpc.py
index e56f5cc2..84e077fa 100644
--- a/tests/test_rpc.py
+++ b/tests/test_rpc.py
@@ -93,3 +93,22 @@ def test_create_spend(minisafed, bitcoind):
     # We can sign it and broadcast it.
     signed_tx_hex = minisafed.sign_psbt(spend_psbt)
     bitcoind.rpc.sendrawtransaction(signed_tx_hex)
+
+
+def test_update_spend(minisafed, bitcoind):
+    # Start by creating a Spend PSBT
+    addr = minisafed.rpc.getnewaddress()["address"]
+    bitcoind.rpc.sendtoaddress(addr, 0.2567)
+    wait_for(lambda: len(minisafed.rpc.listcoins()["coins"]) > 0)
+    outpoints = [c["outpoint"] for c in minisafed.rpc.listcoins()["coins"]]
+    destinations = {
+        bitcoind.rpc.getnewaddress(): 200_000,
+    }
+    res = minisafed.rpc.createspend(outpoints, destinations, 6)
+    assert "psbt" in res
+
+    # Now update it
+    minisafed.rpc.updatespend(res["psbt"])
+
+    # TODO: check it's stored once we implement 'listspendtxs'
+    # TODO: check with added signatures once we implement 'listspendtxs'