diff --git a/ChangeLog b/ChangeLog
index 12a7011b23..a33df5d4f7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2004-10-19  Wolfram Gloger  <wg@malloc.de>
+
+	* malloc/hooks.c (mem2chunk_check, top_check): Handle
+	non-contiguous arena.  Reported by Michael Dalton
+	<mwdalton@stanford.edu> [BZ #457].  Add further checks for top chunk.
+
 2004-12-14  Jakub Jelinek  <jakub@redhat.com>
 
 	* sysdeps/posix/sysconf.c (__sysconf_check_spec): Remove leading
diff --git a/malloc/hooks.c b/malloc/hooks.c
index 8a94fd0be8..a5c97f3133 100644
--- a/malloc/hooks.c
+++ b/malloc/hooks.c
@@ -157,15 +157,16 @@ mem2chunk_check(mem) Void_t* mem;
 
   if(!aligned_OK(mem)) return NULL;
   p = mem2chunk(mem);
-  if( (char*)p>=mp_.sbrk_base &&
-      (char*)p<(mp_.sbrk_base+main_arena.system_mem) ) {
+  if (!chunk_is_mmapped(p)) {
     /* Must be a chunk in conventional heap memory. */
-    if(chunk_is_mmapped(p) ||
-       ( (sz = chunksize(p)),
-	 ((char*)p + sz)>=(mp_.sbrk_base+main_arena.system_mem) ) ||
+    int contig = contiguous(&main_arena);
+    sz = chunksize(p);
+    if((contig &&
+	((char*)p<mp_.sbrk_base ||
+	 ((char*)p + sz)>=(mp_.sbrk_base+main_arena.system_mem) )) ||
        sz<MINSIZE || sz&MALLOC_ALIGN_MASK || !inuse(p) ||
        ( !prev_inuse(p) && (p->prev_size&MALLOC_ALIGN_MASK ||
-                            (long)prev_chunk(p)<(long)mp_.sbrk_base ||
+                            (contig && (char*)prev_chunk(p)<mp_.sbrk_base) ||
                             next_chunk(prev_chunk(p))!=p) ))
       return NULL;
     magic = MAGICBYTE(p);
@@ -213,8 +214,13 @@ top_check()
   INTERNAL_SIZE_T front_misalign, sbrk_size;
   unsigned long pagesz = malloc_getpagesize;
 
-  if((char*)t + chunksize(t) == mp_.sbrk_base + main_arena.system_mem ||
-     t == initial_top(&main_arena)) return 0;
+  if (t == initial_top(&main_arena) ||
+      (!chunk_is_mmapped(t) &&
+       chunksize(t)>=MINSIZE &&
+       prev_inuse(t) &&
+       (!contiguous(&main_arena) ||
+	(char*)t + chunksize(t) == mp_.sbrk_base + main_arena.system_mem)))
+    return 0;
 
   malloc_printerr (check_action, "malloc: top chunk is corrupt", t);