diff --git a/mps/code/arena.c b/mps/code/arena.c
index ce51bcc7e1d..e01adf8dea8 100644
--- a/mps/code/arena.c
+++ b/mps/code/arena.c
@@ -333,7 +333,11 @@ void ArenaDestroy(Arena arena)
     }
     arena->freeCBS.blockPoolStruct.tractList = NULL;
   }
-
+  
+  /* FIXME: Chunks remove their address ranges from the CBS when destroyed,
+     so this is too early.  On the other hand, destroying all the chunks
+     also destroys the CBS's own memory, which might be scattered across
+     chunks by this time, so perhaps this can't be torn down neatly. */
   CBSFinish(&arena->freeCBS);
 
   /* Call class-specific finishing.  This will call ArenaFinish. */
@@ -638,6 +642,29 @@ Res ArenaFreeCBSInsert(Arena arena, Addr base, Addr limit)
 }
 
 
+/* ArenaFreeCBSDelete -- remove a block from free CBS, extending pool if necessary
+ *
+ * See ArenaFreeCBSInsert.
+ */
+
+void ArenaFreeCBSDelete(Arena arena, Addr base, Addr limit)
+{
+  RangeStruct range;
+  Res res;
+  Count nodes;
+
+  RangeInit(&range, base, limit);
+  nodes = arena->freeCBS.splayTreeSize;
+  res = CBSDelete(&range, &arena->freeCBS, &range);
+  
+  /* This should never fail because it is only used to delete whole chunks
+     that are represented by single nodes in the CBS tree. */
+  /* FIXME: Need a better way of checking this. */
+  STATISTIC_STAT(AVER(arena->freeCBS.splayTreeSize == nodes - 1));
+  AVER(res == ResOK);
+}
+
+
 /* arenaAllocFromCBS -- allocate memory using the free CBS
  *
  * The free CBS contains all the free address space we have in chunks,
diff --git a/mps/code/arenavm.c b/mps/code/arenavm.c
index 8bb9159c82c..566697138f5 100644
--- a/mps/code/arenavm.c
+++ b/mps/code/arenavm.c
@@ -333,6 +333,7 @@ static Res VMChunkCreate(Chunk *chunkReturn, VMArena vmArena, Size size)
 
   /* Add the chunk's free address space to the arena's freeCBS, so that
      we can allocate from it. */
+  /* FIXME: Should be in generic ChunkInit so other arenas get the effect. */
   {
     Arena arena = VMArena2Arena(vmArena);
     Chunk chunk = VMChunk2Chunk(vmChunk);
@@ -419,6 +420,11 @@ static void vmChunkDestroy(Chunk chunk)
   AVER(BTIsSetRange(vmChunk->noSparePages, 0, chunk->pageTablePages));
   AVER(BTIsResRange(vmChunk->pageTableMapped, 0, chunk->pageTablePages));
 
+  /* FIXME: Should be in generic ChunkFinish so other arenas get the effect. */
+  ArenaFreeCBSDelete(ChunkArena(chunk),
+                     PageIndexBase(chunk, chunk->allocBase),
+                     chunk->limit);
+
   vmChunk->sig = SigInvalid;
   vm = vmChunk->vm;
   ChunkFinish(chunk);
diff --git a/mps/code/mpm.h b/mps/code/mpm.h
index bc7b353be57..c20cad6b969 100644
--- a/mps/code/mpm.h
+++ b/mps/code/mpm.h
@@ -490,6 +490,7 @@ extern Res ArenaDescribe(Arena arena, mps_lib_FILE *stream);
 extern Res ArenaDescribeTracts(Arena arena, mps_lib_FILE *stream);
 extern Bool ArenaAccess(Addr addr, AccessSet mode, MutatorFaultContext context);
 extern Res ArenaFreeCBSInsert(Arena arena, Addr base, Addr limit);
+extern void ArenaFreeCBSDelete(Arena arena, Addr base, Addr limit);
 
 
 extern Bool GlobalsCheck(Globals arena);
diff --git a/mps/code/mpmst.h b/mps/code/mpmst.h
index 641143ca561..0814930d2b5 100644
--- a/mps/code/mpmst.h
+++ b/mps/code/mpmst.h
@@ -614,7 +614,7 @@ typedef struct GlobalsStruct {
 
 typedef struct CBSStruct {
   SplayTreeStruct splayTree;
-  Count splayTreeSize;
+  STATISTIC_DECL(Count splayTreeSize);
   MFSStruct blockPoolStruct;    /* FIXME: ref to why this is inlined */
   Align alignment;
   Bool fastFind;