diff --git a/src/core/ipv6/ip6_addr.c b/src/core/ipv6/ip6_addr.c
index 6e0ac86b..f8e27987 100644
--- a/src/core/ipv6/ip6_addr.c
+++ b/src/core/ipv6/ip6_addr.c
@@ -96,7 +96,7 @@ ip6addr_aton(const char *cp, ip6_addr_t *addr)
       break;
 #endif /* LWIP_IPV4 */
     } else if (!lwip_isxdigit(*s)) {
-      break;
+      return 0;
     }
   }
 
@@ -166,7 +166,7 @@ ip6addr_aton(const char *cp, ip6_addr_t *addr)
           (u32_t)(10 + (lwip_islower(*s) ? *s - 'a' : *s - 'A')));
     } else {
       /* unexpected digit, space? CRLF? */
-      break;
+      return 0;
     }
   }
 
diff --git a/test/unit/ip6/test_ip6.c b/test/unit/ip6/test_ip6.c
index a030ee5a..f9922aad 100644
--- a/test/unit/ip6/test_ip6.c
+++ b/test/unit/ip6/test_ip6.c
@@ -198,6 +198,8 @@ START_TEST(test_ip6_aton_ipv4mapped)
   const ip_addr_t addr_expected = IPADDR6_INIT_HOST(0, 0, 0xFFFF, 0xD4CC65D2);
   const char *full_ipv6_addr = "0:0:0:0:0:FFFF:D4CC:65D2";
   const char *shortened_ipv6_addr = "::FFFF:D4CC:65D2";
+  const char *shortened_ipv6_addr_unexpected_char = "::FFFF:D4CC:65DZ";
+  const char *shortened_ipv6_addr_invalid = "::GGGGGGGG";
   const char *full_ipv4_mapped_addr = "0:0:0:0:0:FFFF:212.204.101.210";
   const char *shortened_ipv4_mapped_addr = "::FFFF:212.204.101.210";
   const char *bogus_ipv4_mapped_addr = "::FFFF:212.204.101.2101";
@@ -223,6 +225,16 @@ START_TEST(test_ip6_aton_ipv4mapped)
   fail_unless(ret == 1);
   fail_unless(memcmp(&addr, &addr_expected, 16) == 0);
 
+  /* check shortened IPv6 with unexpected char */
+  memset(&addr6, 0, sizeof(addr6));
+  ret = ip6addr_aton(shortened_ipv6_addr_unexpected_char, &addr6);
+  fail_unless(ret == 0);
+
+  /* check shortened IPv6 that is clearly invalid */
+  memset(&addr6, 0, sizeof(addr6));
+  ret = ip6addr_aton(shortened_ipv6_addr_invalid, &addr6);
+  fail_unless(ret == 0);
+
   /* checked shortened mixed representation */
   memset(&addr6, 0, sizeof(addr6));
   ret = ip6addr_aton(shortened_ipv4_mapped_addr, &addr6);