diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index a89cb52228c2ccf14d7df0317b646f30f407610e..55473371b7c6934abe8486af6fc3055701187140 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -26,6 +26,7 @@
 #include <linux/backing-dev.h>
 #include <linux/bootmem.h>
 #include <linux/pipe_fs_i.h>
+#include <linux/pfn.h>
 
 #include <asm/uaccess.h>
 #include <asm/io.h>