diff --git a/include/asm-s390/compat.h b/include/asm-s390/compat.h
index a007715f4aea..356a0b183539 100644
--- a/include/asm-s390/compat.h
+++ b/include/asm-s390/compat.h
@@ -128,6 +128,11 @@ static inline void __user *compat_ptr(compat_uptr_t uptr)
 	return (void __user *)(unsigned long)(uptr & 0x7fffffffUL);
 }
 
+static inline compat_uptr_t ptr_to_compat(void __user *uptr)
+{
+	return (u32)(unsigned long)uptr;
+}
+
 static inline void __user *compat_alloc_user_space(long len)
 {
 	unsigned long stack;