diff -ru lwip/src/core/mem.c lwip-patched/src/core/mem.c
--- lwip/src/core/mem.c	2007-09-15 13:34:06.000000000 +0200
+++ lwip-patched/src/core/mem.c	2007-10-08 16:41:25.008750000 +0200
@@ -341,6 +341,9 @@
     next = mem2->next;
     /* create new struct mem which is moved directly after the shrinked mem */
     ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
+    if (lfree == mem2) {
+      lfree = (struct mem *)&ram[ptr2];
+    }
     mem2 = (struct mem *)&ram[ptr2];
     mem2->used = 0;
     /* restore the next pointer */