diff --git a/sample-app/src/main/java/at/bitfire/cert4android/demo/MainActivity.kt b/sample-app/src/main/java/at/bitfire/cert4android/demo/MainActivity.kt
index 6f4e43f..3802994 100644
--- a/sample-app/src/main/java/at/bitfire/cert4android/demo/MainActivity.kt
+++ b/sample-app/src/main/java/at/bitfire/cert4android/demo/MainActivity.kt
@@ -179,6 +179,7 @@ class MainActivity : ComponentActivity() {
         private val _certificateFlow = MutableStateFlow<X509Certificate?>(null)
         val certificateFlow: StateFlow<X509Certificate?> = _certificateFlow
 
+        @Volatile
         private var userDecision: CompletableDeferred<Boolean> = CompletableDeferred()
 
         fun setUserDecision(decision: Boolean) {