diff --git a/arch/um/kernel/physmem.c b/arch/um/kernel/physmem.c
index a55d221..1fe86d8 100644
--- a/arch/um/kernel/physmem.c
+++ b/arch/um/kernel/physmem.c
@@ -115,7 +115,7 @@
 		     len - bootmap_size - reserve);
 }
 
-int phys_mapping(unsigned long phys, __u64 *offset_out)
+int phys_mapping(unsigned long phys, unsigned long long *offset_out)
 {
 	int fd = -1;