diff --git a/src/multimedia/audio/qaudiosystem.h b/src/multimedia/audio/qaudiosystem.h
index 2eeb9152..0f253e1a 100644
--- a/src/multimedia/audio/qaudiosystem.h
+++ b/src/multimedia/audio/qaudiosystem.h
@@ -43,6 +43,8 @@
 
 QT_BEGIN_NAMESPACE
 
+class QIODevice;
+
 // Required for QDoc workaround
 class QString;