diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -999,7 +999,7 @@
 		    int fd,
 		    _Out_writes_bytes_(count) char *buf,
 		    u_int count,
-		    _Out_ long *basep
+		    _Out_opt_ long *basep
 		);
 	}
 157	AUE_STATFS	COMPAT4 {
@@ -1185,7 +1185,7 @@
 		    int fd,
 		    _Out_writes_bytes_(count) char *buf,
 		    u_int count,
-		    _Out_ long *basep
+		    _Out_opt_ long *basep
 		);
 	}
 197	AUE_MMAP	COMPAT6|CAPENABLED {
@@ -3097,7 +3097,7 @@
 		    int fd,
 		    _Out_writes_bytes_(count) char *buf,
 		    size_t count,
-		    _Out_ off_t *basep
+		    _Out_opt_ off_t *basep
 		);
 	}
 555	AUE_STATFS	STD {