diff --git a/client/src/main/java/ctbrec/ui/ExternalBrowser.java b/client/src/main/java/ctbrec/ui/ExternalBrowser.java
index e7b896ca..a4801e06 100644
--- a/client/src/main/java/ctbrec/ui/ExternalBrowser.java
+++ b/client/src/main/java/ctbrec/ui/ExternalBrowser.java
@@ -12,6 +12,7 @@ import java.net.Socket;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Optional;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.locks.Lock;
@@ -78,7 +79,7 @@ public class ExternalBrowser implements AutoCloseable {
             out.write('\n');
             out.flush();
 
-            onReadyCallback.run();
+            Optional.ofNullable(onReadyCallback).ifPresent(Runnable::run);
 
             LOG.debug("Waiting for browser to terminate");
             p.waitFor();