diff --git a/Headers/gnustep/gui/AppKit.h b/Headers/gnustep/gui/AppKit.h
index 34e1e318c..d88bc7145 100644
--- a/Headers/gnustep/gui/AppKit.h
+++ b/Headers/gnustep/gui/AppKit.h
@@ -137,6 +137,7 @@
 #include <AppKit/NSLayoutManager.h>
 #include <AppKit/NSTextContainer.h>
 #include <AppKit/NSTextStorage.h>
+#include <AppKit/NSUserInterfaceValidation.h>
 #include <AppKit/NSWindowController.h>
 #endif