diff --git a/ip2net/ip2net.c b/ip2net/ip2net.c
index 6243a47..ee57fd7 100644
--- a/ip2net/ip2net.c
+++ b/ip2net/ip2net.c
@@ -184,7 +184,7 @@ static void parse_params(int argc, char *argv[])
 		case 4:
 			i = sscanf(optarg,"%u-%u",&plen1,&plen2);
 			if (i == 1) plen2 = plen1;
-			if (!i || plen2<plen1 || !plen1 || !plen2)
+			if (i<=0 || plen2<plen1 || !plen1 || !plen2)
 			{
 				fprintf(stderr, "invalid parameter for prefix-length : %s\n", optarg);
 				exit(1);
@@ -245,17 +245,15 @@ int main(int argc, char **argv)
 				{
 					// we have subnet ip6/y
 					// output it as is
-					*s = d;
-					if (sscanf(s + 1, "%u", &zct) && zct!=128)
+					if (sscanf(s + 1, "%u", &zct)==1 && zct!=128)
 					{
-						if (zct<128) printf("%s\n", str);
+						if (zct<128) printf("%s/%u\n", str, zct);
 						continue;
 					}
 				}
 				else if (d=='-')
 				{
-					*s = d;
-					if (inet_pton(AF_INET6, s+1, &a)) printf("%s\n", str);
+					if (inet_pton(AF_INET6, s+1, &a)) printf("%s-%s\n", str, s+1);
 					continue;
 				}
 				if (ipct >= iplist_size)
diff --git a/mdig/mdig.c b/mdig/mdig.c
index b50d95a..9728789 100644
--- a/mdig/mdig.c
+++ b/mdig/mdig.c
@@ -204,7 +204,7 @@ static void *t_resolver(void *arg)
 					bool mask_needed = false;
 					if (s_mask)
 					{
-						if (sscanf(s_mask, "%u", &mask))
+						if (sscanf(s_mask, "%u", &mask)==1)
 						{
 							switch (family)
 							{
diff --git a/tpws/tpws.c b/tpws/tpws.c
index afef457..06cbade 100644
--- a/tpws/tpws.c
+++ b/tpws/tpws.c
@@ -348,7 +348,7 @@ void parse_params(int argc, char *argv[])
 		case 13: /* uid */
 			params.gid=0x7FFFFFFF; // default git. drop gid=0
 			params.droproot = true;
-			if (!sscanf(optarg,"%u:%u",&params.uid,&params.gid))
+			if (sscanf(optarg,"%u:%u",&params.uid,&params.gid)<1)
 			{
 				fprintf(stderr, "--uid should be : uid[:gid]\n");
 				exit_clean(1);