diff --git a/kcm/headers.h b/kcm/headers.h
index 8d6bd5ab8..d42ccefe1 100644
--- a/kcm/headers.h
+++ b/kcm/headers.h
@@ -69,6 +69,7 @@
 #endif
 #ifdef HAVE_DOOR_CREATE
 #include <door.h>
+#include <alloca.h>
 #endif
 #include <err.h>
 #include <roken.h>