diff --git a/src/support/debug.cxx b/src/support/debug.cxx
index 1d2eb4b6..de8e5a16 100644
--- a/src/support/debug.cxx
+++ b/src/support/debug.cxx
@@ -186,8 +186,8 @@ void debug::show(void)
 
 void debug::sync_text(void* arg)
 {
-	if (!window->visible())
-		return;
+	if (!window) return;
+	if (!window->visible()) return;
 
 	guard_lock dlock(&debug_mutex);
 	if (inst == 0 || btext == 0) return;