diff --git a/src/locale/haiku/SDL_syslocale.cc b/src/locale/haiku/SDL_syslocale.cc
index a0885fa42..3b930e8bc 100644
--- a/src/locale/haiku/SDL_syslocale.cc
+++ b/src/locale/haiku/SDL_syslocale.cc
@@ -19,6 +19,7 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
+#include <AppKit.h>
 #include <LocaleRoster.h>
 #include <TypeConstants.h>