diff --git a/CHANGELOG b/CHANGELOG
index c9c0799d..7114fd9f 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -405,6 +405,9 @@ HISTORY
 
   ++ Bug fixes:
 
+  2007-09-19 Simon Goldschmidt
+  * icmp.c: Fixed bug #21107 (didn't reset IP TTL in ICMP echo replies)
+
   2007-09-06 Frédéric Bernon
   * several-files: replace some #include "arch/cc.h" by "lwip/arch.h", or simply remove
     it as long as "lwip/opt.h" is included before (this one include "lwip/debug.h" which
diff --git a/src/core/ipv4/icmp.c b/src/core/ipv4/icmp.c
index e9dec868..8f03d3a2 100644
--- a/src/core/ipv4/icmp.c
+++ b/src/core/ipv4/icmp.c
@@ -163,6 +163,14 @@ icmp_input(struct pbuf *p, struct netif *inp)
     } else {
       iecho->chksum += htons(ICMP_ECHO << 8);
     }
+
+    /* Set the correct TTL and recalculate the header checksum. */
+    IPH_TTL_SET(iphdr, ICMP_TTL);
+    IPH_CHKSUM_SET(iphdr, 0);
+#if CHECKSUM_GEN_IP
+    IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
+#endif /* CHECKSUM_GEN_IP */
+
     ICMP_STATS_INC(icmp.xmit);
     /* increase number of messages attempted to send */
     snmp_inc_icmpoutmsgs();