diff --git a/src/firmware/FlashButton.tsx b/src/firmware/FlashButton.tsx
index 89e73804..c8d5d4b0 100644
--- a/src/firmware/FlashButton.tsx
+++ b/src/firmware/FlashButton.tsx
@@ -2,6 +2,7 @@
 // Copyright (c) 2020-2021 The Pybricks Authors
 
 import { connect } from 'react-redux';
+import { HubRuntimeState } from '../hub/reducers';
 import { BootloaderConnectionState } from '../lwp3-bootloader/reducers';
 import * as notification from '../notifications/actions';
 import { RootState } from '../reducers';
@@ -19,7 +20,9 @@ type OwnProps = Pick<OpenFileButtonProps, 'id'>;
 
 const mapStateToProps = (state: RootState): StateProps => ({
     tooltip: state.firmware.flashing ? TooltipId.FlashProgress : TooltipId.Flash,
-    enabled: state.bootloader.connection === BootloaderConnectionState.Disconnected,
+    enabled:
+        state.bootloader.connection === BootloaderConnectionState.Disconnected &&
+        state.hub.runtime === HubRuntimeState.Disconnected,
     showProgress: state.firmware.flashing,
     progress: state.firmware.progress === null ? undefined : state.firmware.progress,
 });