diff --git a/arch/um/sys-x86_64/syscalls.c b/arch/um/sys-x86_64/syscalls.c
index 6acee5c4ada..6fce9f45dfd 100644
--- a/arch/um/sys-x86_64/syscalls.c
+++ b/arch/um/sys-x86_64/syscalls.c
@@ -45,7 +45,7 @@ static long arch_prctl_tt(int code, unsigned long addr)
 	case ARCH_GET_GS:
 		ret = arch_prctl(code, (unsigned long) &tmp);
 		if(!ret)
-			ret = put_user(tmp, &addr);
+			ret = put_user(tmp, (long __user *)addr);
 		break;
 	default:
 		ret = -EINVAL;