diff --git a/lib/libsys/_libsys.h b/lib/libsys/_libsys.h
--- a/lib/libsys/_libsys.h
+++ b/lib/libsys/_libsys.h
@@ -141,8 +141,8 @@
 typedef int (__sys_gettimeofday_t)(struct timeval *, struct timezone *);
 typedef int (__sys_getrusage_t)(int, struct rusage *);
 typedef int (__sys_getsockopt_t)(int, int, int, void *, __socklen_t *);
-typedef int (__sys_readv_t)(int, const struct iovec *, u_int);
-typedef int (__sys_writev_t)(int, const struct iovec *, u_int);
+typedef ssize_t (__sys_readv_t)(int, const struct iovec *, u_int);
+typedef ssize_t (__sys_writev_t)(int, const struct iovec *, u_int);
 typedef int (__sys_settimeofday_t)(const struct timeval *, const struct timezone *);
 typedef int (__sys_fchown_t)(int, int, int);
 typedef int (__sys_fchmod_t)(int, mode_t);
@@ -540,8 +540,8 @@
 int __sys_gettimeofday(struct timeval * tp, struct timezone * tzp);
 int __sys_getrusage(int who, struct rusage * rusage);
 int __sys_getsockopt(int s, int level, int name, void * val, __socklen_t * avalsize);
-int __sys_readv(int fd, const struct iovec * iovp, u_int iovcnt);
-int __sys_writev(int fd, const struct iovec * iovp, u_int iovcnt);
+ssize_t __sys_readv(int fd, const struct iovec * iovp, u_int iovcnt);
+ssize_t __sys_writev(int fd, const struct iovec * iovp, u_int iovcnt);
 int __sys_settimeofday(const struct timeval * tv, const struct timezone * tzp);
 int __sys_fchown(int fd, int uid, int gid);
 int __sys_fchmod(int fd, mode_t mode);
diff --git a/sys/compat/freebsd32/freebsd32_systrace_args.c b/sys/compat/freebsd32/freebsd32_systrace_args.c
--- a/sys/compat/freebsd32/freebsd32_systrace_args.c
+++ b/sys/compat/freebsd32/freebsd32_systrace_args.c
@@ -9473,12 +9473,12 @@
 	/* freebsd32_readv */
 	case 120:
 		if (ndx == 0 || ndx == 1)
-			p = "int";
+			p = "ssize_t";
 		break;
 	/* freebsd32_writev */
 	case 121:
 		if (ndx == 0 || ndx == 1)
-			p = "int";
+			p = "ssize_t";
 		break;
 	/* freebsd32_settimeofday */
 	case 122:
diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -782,14 +782,14 @@
 	}
 119	AUE_NULL	RESERVED
 120	AUE_READV	STD|CAPENABLED {
-		int readv(
+		ssize_t readv(
 		    int fd,
 		    _In_reads_(iovcnt) _Contains_long_ptr_ const struct iovec *iovp,
 		    u_int iovcnt
 		);
 	}
 121	AUE_WRITEV	STD|CAPENABLED {
-		int writev(
+		ssize_t writev(
 		    int fd,
 		    _In_reads_(iovcnt) _Contains_long_ptr_ const struct iovec *iovp,
 		    u_int iovcnt
diff --git a/sys/kern/systrace_args.c b/sys/kern/systrace_args.c
--- a/sys/kern/systrace_args.c
+++ b/sys/kern/systrace_args.c
@@ -9618,12 +9618,12 @@
 	/* readv */
 	case 120:
 		if (ndx == 0 || ndx == 1)
-			p = "int";
+			p = "ssize_t";
 		break;
 	/* writev */
 	case 121:
 		if (ndx == 0 || ndx == 1)
-			p = "int";
+			p = "ssize_t";
 		break;
 	/* settimeofday */
 	case 122: