diff --git a/src/core/ipv4/dhcp.c b/src/core/ipv4/dhcp.c
index ecf19bdb..b17fd779 100644
--- a/src/core/ipv4/dhcp.c
+++ b/src/core/ipv4/dhcp.c
@@ -1519,7 +1519,7 @@ again:
         break;
       case(DHCP_OPTION_DNS_SERVER):
         /* special case: there might be more than one server */
-        LWIP_ERROR("len % 4 == 0", len % 4 == 0, return ERR_VAL;);
+        LWIP_ERROR("len %% 4 == 0", len % 4 == 0, return ERR_VAL;);
         /* limit number of DNS servers */
         decode_len = LWIP_MIN(len, 4 * DNS_MAX_SERVERS);
         LWIP_ERROR("len >= decode_len", len >= decode_len, return ERR_VAL;);
@@ -1532,7 +1532,7 @@ again:
 #if LWIP_DHCP_GET_NTP_SRV
       case(DHCP_OPTION_NTP):
         /* special case: there might be more than one server */
-        LWIP_ERROR("len % 4 == 0", len % 4 == 0, return ERR_VAL;);
+        LWIP_ERROR("len %% 4 == 0", len % 4 == 0, return ERR_VAL;);
         /* limit number of NTP servers */
         decode_len = LWIP_MIN(len, 4 * LWIP_DHCP_MAX_NTP_SERVERS);
         LWIP_ERROR("len >= decode_len", len >= decode_len, return ERR_VAL;);
@@ -1577,7 +1577,7 @@ decode_next:
         }
         if (decode_len > 4) {
           /* decode more than one u32_t */
-          LWIP_ERROR("decode_len % 4 == 0", decode_len % 4 == 0, return ERR_VAL;);
+          LWIP_ERROR("decode_len %% 4 == 0", decode_len % 4 == 0, return ERR_VAL;);
           dhcp_got_option(dhcp, decode_idx);
           dhcp_set_option_value(dhcp, decode_idx, lwip_htonl(value));
           decode_len -= 4;