diff --git a/sys/compat/linuxkpi/common/include/linux/idr.h b/sys/compat/linuxkpi/common/include/linux/idr.h
--- a/sys/compat/linuxkpi/common/include/linux/idr.h
+++ b/sys/compat/linuxkpi/common/include/linux/idr.h
@@ -34,6 +34,7 @@
 #include <sys/limits.h>
 #include <sys/mutex.h>
 
+#include <linux/radix-tree.h>
 #include <linux/gpf.h>
 #include <linux/types.h>
 
diff --git a/sys/compat/linuxkpi/common/include/linux/radix-tree.h b/sys/compat/linuxkpi/common/include/linux/radix-tree.h
--- a/sys/compat/linuxkpi/common/include/linux/radix-tree.h
+++ b/sys/compat/linuxkpi/common/include/linux/radix-tree.h
@@ -29,6 +29,7 @@
 #ifndef	_LINUXKPI_LINUX_RADIX_TREE_H_
 #define	_LINUXKPI_LINUX_RADIX_TREE_H_
 
+#include <linux/rcupdate.h>
 #include <linux/types.h>
 
 #define	RADIX_TREE_MAP_SHIFT	6