diff --git a/netutils/netlib/netlib_ipv4route.c b/netutils/netlib/netlib_ipv4route.c
index 03a14ca22..86fb83e68 100644
--- a/netutils/netlib/netlib_ipv4route.c
+++ b/netutils/netlib/netlib_ipv4route.c
@@ -84,6 +84,8 @@
 
 static void set_nul_terminator(FAR char *str)
 {
+   /* The first non-decimal character that is not '.' terminates the address */
+
    while ((*str >= '0' && *str <= '9') || *str == '.')
      {
        str++;
diff --git a/netutils/netlib/netlib_ipv6route.c b/netutils/netlib/netlib_ipv6route.c
index af8375fe5..82d7d0ab0 100644
--- a/netutils/netlib/netlib_ipv6route.c
+++ b/netutils/netlib/netlib_ipv6route.c
@@ -83,7 +83,12 @@
 
 static void set_nul_terminator(FAR char *str)
 {
-   while ((*str >= '0' && *str <= '9') || *str == '.')
+   /* The first non-hex character that is not ':' terminates the address */
+
+   while ((*str >= '0' && *str <= '9') ||
+          (*str >= 'a' && *str <= 'f') ||
+          (*str >= 'A' && *str <= 'F') ||
+           *str == ':')
      {
        str++;
      }