diff --git a/lib/connector/meshcore_connector.dart b/lib/connector/meshcore_connector.dart
index 7b46c113..d4d914bc 100644
--- a/lib/connector/meshcore_connector.dart
+++ b/lib/connector/meshcore_connector.dart
@@ -4795,8 +4795,11 @@ class MeshCoreConnector extends ChangeNotifier {
         'cannot derive a transport key for region "$regionName"',
       );
     }
-    await setChannelSendScope(key);
     try {
+      // Inside the try so a lost ack on the set (the firmware may already have
+      // applied the scope) still runs the clear below, rather than leaking the
+      // scope onto the next unscoped send.
+      await setChannelSendScope(key);
       await sendFrame(
         frame,
         channelSendQueueId: channelSendQueueId,
diff --git a/test/connector/channel_scope_send_test.dart b/test/connector/channel_scope_send_test.dart
index d1912c43..404da8a9 100644
--- a/test/connector/channel_scope_send_test.dart
+++ b/test/connector/channel_scope_send_test.dart
@@ -69,4 +69,19 @@ void main() {
       expect(sent, isEmpty);
     },
   );
+
+  test('a failed set-scope still attempts a clear (no scope leak)', () async {
+    await connector.channelRegionScopeStoreForTest.setScope(0, 'oki');
+    var calls = 0;
+    connector.sendFrameOverrideForTest = (_) {
+      calls++;
+      if (calls == 1) throw Exception('lost ack on set-scope');
+    };
+    await expectLater(
+      connector.sendChannelFrameScopedForTest(0, frame),
+      throwsA(isA<Exception>()),
+    );
+    // call 1 = set-scope (threw); call 2 = clear-scope run from the finally.
+    expect(calls, 2);
+  });
 }