diff --git a/src/api/pool.js b/src/api/pool.js
index e00c7eee5..08e414946 100644
--- a/src/api/pool.js
+++ b/src/api/pool.js
@@ -1,3 +1,4 @@
+import {JsonRpcError} from '../api-errors'
 import {extractProperty} from '../utils'
 
 // ===================================================================
@@ -80,7 +81,12 @@ export {uploadPatch as patch}
 // -------------------------------------------------------------------
 
 export async function mergeInto ({ source, target, force }) {
-  await this.mergeXenPools(source.id, target.id, force)
+  try {
+    await this.mergeXenPools(source.id, target.id, force)
+  } catch (e) {
+    // FIXME: should we expose plain XAPI error messages?
+    throw new JsonRpcError(e.message)
+  }
 }
 
 mergeInto.params = {
diff --git a/src/xo.js b/src/xo.js
index a3cfb79ea..c54a0c54d 100644
--- a/src/xo.js
+++ b/src/xo.js
@@ -881,10 +881,10 @@ export default class Xo extends EventEmitter {
     return xapi
   }
 
-  async mergeXenPools (sourceId, targetId) {
+  async mergeXenPools (sourceId, targetId, force = false) {
     const sourceXapi = this.getXAPI(sourceId)
     const {
-      _auth: { username, password },
+      _auth: { user, password },
       _url: { hostname }
     } = this.getXAPI(targetId)
 
@@ -903,7 +903,7 @@ export default class Xo extends EventEmitter {
     }
 
     try {
-      await sourceXapi.joinPool(hostname, username, password)
+      await sourceXapi.joinPool(hostname, user, password, force)
     } finally {
       await this.disconnectXenServer(sourceId)
     }