diff --git a/lib/network.c b/lib/network.c
index b68761b..d105db4 100644
--- a/lib/network.c
+++ b/lib/network.c
@@ -24,7 +24,7 @@
 
 /* Read nbytes from fd and store into ptr. */
 int
-readn (int fd, char *ptr, int nbytes)
+readn (int fd, u_char *ptr, int nbytes)
 {
   int nleft;
   int nread;
@@ -50,7 +50,7 @@
 
 /* Write nbytes from ptr to fd. */
 int
-writen(int fd, char *ptr, int nbytes)
+writen(int fd, u_char *ptr, int nbytes)
 {
   int nleft;
   int nwritten;