diff --git a/io.c b/io.c
index 7500994..35a3110 100644
--- a/io.c
+++ b/io.c
@@ -743,16 +743,18 @@ int st_sendmsg(_st_netfd_t *fd, const struct msghdr *msg, int flags, st_utime_t
 }
 
 
-#if defined(MD_HAVE_SENDMMSG) && defined(_GNU_SOURCE)
-int st_sendmmsg(st_netfd_t fd, struct mmsghdr *msgvec, unsigned int vlen, int flags, st_utime_t timeout)
+int st_sendmmsg(st_netfd_t fd, void *msgvec, unsigned int vlen, int flags, st_utime_t timeout)
 {
+#if !defined(MD_HAVE_SENDMMSG) || !defined(_GNU_SOURCE)
+    return -1;
+#else
     int n;
     int left;
     struct mmsghdr *p;
 
     left = (int)vlen;
     while (left > 0) {
-        p = msgvec + (vlen - left);
+        p = (struct mmsghdr*)msgvec + (vlen - left);
 
         if ((n = sendmmsg(fd->osfd, p, left, flags)) < 0) {
             if (errno == EINTR)
@@ -772,8 +774,8 @@ int st_sendmmsg(st_netfd_t fd, struct mmsghdr *msgvec, unsigned int vlen, int fl
         return n;
     }
     return (int)vlen - left;
-}
 #endif
+}
 
 
 /*
diff --git a/public.h b/public.h
index c54bd79..a581adc 100644
--- a/public.h
+++ b/public.h
@@ -151,7 +151,7 @@ extern int st_recvfrom(st_netfd_t fd, void *buf, int len, struct sockaddr *from,
 extern int st_sendto(st_netfd_t fd, const void *msg, int len, const struct sockaddr *to, int tolen, st_utime_t timeout);
 extern int st_recvmsg(st_netfd_t fd, struct msghdr *msg, int flags, st_utime_t timeout);
 extern int st_sendmsg(st_netfd_t fd, const struct msghdr *msg, int flags, st_utime_t timeout);
-extern int st_sendmmsg(st_netfd_t fd, struct mmsghdr *msgvec, unsigned int vlen, int flags, st_utime_t timeout);
+extern int st_sendmmsg(st_netfd_t fd, void *msgvec, unsigned int vlen, int flags, st_utime_t timeout);
 extern st_netfd_t st_open(const char *path, int oflags, mode_t mode);
 
 #ifdef DEBUG