diff --git a/ChangeLog b/ChangeLog
index 4028db2fd9..2989d21940 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2016-06-11  Florian Weimer  <fweimer@redhat.com>
+
+	* malloc/malloc.c (musable): Return correct size for dumped fake
+	mmapped chunk.
+
 2016-06-11  Florian Weimer  <fweimer@redhat.com>
 
 	[BZ #20222]
diff --git a/malloc/malloc.c b/malloc/malloc.c
index ac0f751593..21a912a6d1 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -4622,7 +4622,12 @@ musable (void *mem)
         return malloc_check_get_size (p);
 
       if (chunk_is_mmapped (p))
-        return chunksize (p) - 2 * SIZE_SZ;
+	{
+	  if (DUMPED_MAIN_ARENA_CHUNK (p))
+	    return chunksize (p) - SIZE_SZ;
+	  else
+	    return chunksize (p) - 2 * SIZE_SZ;
+	}
       else if (inuse (p))
         return chunksize (p) - SIZE_SZ;
     }