diff --git a/arch/um/sys-i386/syscalls.c b/arch/um/sys-i386/syscalls.c
index 749dd1b..710d5fb 100644
--- a/arch/um/sys-i386/syscalls.c
+++ b/arch/um/sys-i386/syscalls.c
@@ -99,11 +99,12 @@
 
 	switch (call) {
 	case SEMOP:
-		return sys_semtimedop(first, (struct sembuf *) ptr, second,
-				      NULL);
+		return sys_semtimedop(first, (struct sembuf __user *) ptr,
+				      second, NULL);
 	case SEMTIMEDOP:
-		return sys_semtimedop(first, (struct sembuf *) ptr, second,
-				      (const struct timespec *) fifth);
+		return sys_semtimedop(first, (struct sembuf __user *) ptr,
+				      second,
+				      (const struct timespec __user *) fifth);
 	case SEMGET:
 		return sys_semget (first, second, third);
 	case SEMCTL: {