Index: orig/libavformat/matroskadec.c
===================================================================
--- orig/libavformat/matroskadec.c	(revision 105133)
+++ ffmpeg/libavformat/matroskadec.c	(working copy)
@@ -1841,7 +1841,7 @@
                         lace_size[n] = lace_size[n - 1] + snum;
                         total += lace_size[n];
                     }
-                    lace_size[n] = size - total;
+                    lace_size[laces - 1] = size - total;
                     break;
                 }
             }