diff --git a/scsh/network1.h b/scsh/network1.h
index 729c79f..05ed1ab 100644
--- a/scsh/network1.h
+++ b/scsh/network1.h
@@ -13,9 +13,9 @@ int scheme_socket_name(int sockfd, int family, s48_value scheme_name);
 int scheme_socket_pair(int type, int *s1, int *s2);
 
 int recv_substring(int s, int flags, s48_value buf, 
-		   int start, int end, s48_value scheme_name);
+		   size_t start, size_t end, s48_value scheme_name);
 
-int send_substring(int s, int flags, s48_value buf, int start, int end,
+int send_substring(int s, int flags, s48_value buf, size_t start, size_t end,
 		   int family, s48_value scheme_name);
 
 int scheme_getsockopt (int s, int level, int optname);