diff --git a/src/api/netdb.c b/src/api/netdb.c
index 6a4bac56..9f38ef91 100644
--- a/src/api/netdb.c
+++ b/src/api/netdb.c
@@ -314,7 +314,7 @@ lwip_getaddrinfo(const char *nodename, const char *servname,
     total_size <= NETDB_ELEM_SIZE);
   ai = (struct addrinfo *)memp_malloc(MEMP_NETDB);
   if (ai == NULL) {
-    goto memerr;
+    return EAI_MEMORY;
   }
   memset(ai, 0, total_size);
   sa = (struct sockaddr_in*)((u8_t*)ai + sizeof(struct addrinfo));
@@ -343,11 +343,6 @@ lwip_getaddrinfo(const char *nodename, const char *servname,
   *res = ai;
 
   return 0;
-memerr:
-  if (ai != NULL) {
-    memp_free(MEMP_NETDB, ai);
-  }
-  return EAI_MEMORY;
 }
 
 #endif /* LWIP_DNS && LWIP_SOCKET */
diff --git a/src/core/ipv4/igmp.c b/src/core/ipv4/igmp.c
index 2e79f545..6db7f913 100644
--- a/src/core/ipv4/igmp.c
+++ b/src/core/ipv4/igmp.c
@@ -704,6 +704,9 @@ igmp_start_timer(struct igmp_group *group, u8_t max_time)
   }
   /* ensure the random value is > 0 */
   group->timer = (LWIP_RAND() % max_time);
+  if (group->timer == 0) {
+    group->timer = 1;
+  }
 #else /* LWIP_RAND */
   /* ATTENTION: use this only if absolutely necessary! */
   group->timer = max_time / 2;
diff --git a/src/core/ipv6/mld6.c b/src/core/ipv6/mld6.c
index 78c3776a..0771f5c8 100644
--- a/src/core/ipv6/mld6.c
+++ b/src/core/ipv6/mld6.c
@@ -496,7 +496,10 @@ mld6_delayed_report(struct mld_group *group, u16_t maxresp)
 
 #ifdef LWIP_RAND
   /* Randomize maxresp. (if LWIP_RAND is supported) */
-  maxresp = (LWIP_RAND() % (maxresp - 1)) + 1;
+  maxresp = LWIP_RAND() % maxresp;
+  if (maxresp == 0) {
+    maxresp = 1;
+  }
 #endif /* LWIP_RAND */
 
   /* Apply timer value if no report has been scheduled already. */
diff --git a/src/core/ipv6/nd6.c b/src/core/ipv6/nd6.c
index da373bd3..7c65df36 100644
--- a/src/core/ipv6/nd6.c
+++ b/src/core/ipv6/nd6.c
@@ -455,24 +455,25 @@ nd6_input(struct pbuf *p, struct netif *inp)
 
         if (prefix_opt->flags & ND6_PREFIX_FLAG_ON_LINK) {
           /* Add to on-link prefix list. */
+          s8_t prefix;
 
           /* Get a memory-aligned copy of the prefix. */
           ip6_addr_set(ip6_current_dest_addr(), &(prefix_opt->prefix));
 
           /* find cache entry for this prefix. */
-          i = nd6_get_onlink_prefix(ip6_current_dest_addr(), inp);
-          if (i < 0) {
+          prefix = nd6_get_onlink_prefix(ip6_current_dest_addr(), inp);
+          if (prefix < 0) {
             /* Create a new cache entry. */
-            i = nd6_new_onlink_prefix(ip6_current_dest_addr(), inp);
+            prefix = nd6_new_onlink_prefix(ip6_current_dest_addr(), inp);
           }
-          if (i >= 0) {
-            prefix_list[i].invalidation_timer = prefix_opt->valid_lifetime;
+          if (prefix >= 0) {
+            prefix_list[prefix].invalidation_timer = prefix_opt->valid_lifetime;
 
 #if LWIP_IPV6_AUTOCONFIG
             if (prefix_opt->flags & ND6_PREFIX_FLAG_AUTONOMOUS) {
               /* Mark prefix as autonomous, so that address autoconfiguration can take place.
                * Only OR flag, so that we don't over-write other flags (such as ADDRESS_DUPLICATE)*/
-              prefix_list[i].flags |= ND6_PREFIX_AUTOCONFIG_AUTONOMOUS;
+              prefix_list[prefix].flags |= ND6_PREFIX_AUTOCONFIG_AUTONOMOUS;
             }
 #endif /* LWIP_IPV6_AUTOCONFIG */
           }