diff --git a/mps/code/arena.c b/mps/code/arena.c
index 3a41ebbb0df..05279ab6bd6 100644
--- a/mps/code/arena.c
+++ b/mps/code/arena.c
@@ -91,7 +91,6 @@ DEFINE_CLASS(AbstractArenaClass, class)
   class->free = NULL;
   class->chunkInit = NULL;
   class->chunkFinish = NULL;
-  class->chunkReserved = NULL;
   class->compact = ArenaTrivCompact;
   class->describe = ArenaTrivDescribe;
   class->pagesMarkAllocated = NULL;
@@ -119,7 +118,6 @@ Bool ArenaClassCheck(ArenaClass class)
   CHECKL(FUNCHECK(class->free));
   CHECKL(FUNCHECK(class->chunkInit));
   CHECKL(FUNCHECK(class->chunkFinish));
-  CHECKL(FUNCHECK(class->chunkReserved));
   CHECKL(FUNCHECK(class->compact));
   CHECKL(FUNCHECK(class->describe));
   CHECKL(FUNCHECK(class->pagesMarkAllocated));
@@ -669,7 +667,6 @@ Res ControlDescribe(Arena arena, mps_lib_FILE *stream, Count depth)
 void ArenaChunkInsert(Arena arena, Chunk chunk) {
   Bool inserted;
   Tree tree, updatedTree = NULL;
-  Size size;
 
   AVERT(Arena, arena);
   AVERT(Chunk, chunk);
@@ -683,8 +680,7 @@ void ArenaChunkInsert(Arena arena, Chunk chunk) {
   arena->chunkTree = updatedTree;
   RingAppend(&arena->chunkRing, &chunk->arenaRing);
 
-  size = (*arena->class->chunkReserved)(chunk);
-  arena->reserved += size;
+  arena->reserved += ChunkReserved(chunk);
 
   /* As part of the bootstrap, the first created chunk becomes the primary
      chunk.  This step allows ArenaFreeLandInsert to allocate pages. */
@@ -708,7 +704,7 @@ void ArenaChunkRemoved(Arena arena, Chunk chunk)
   if (arena->primary == chunk)
     arena->primary = NULL;
 
-  size = (*arena->class->chunkReserved)(chunk);
+  size = ChunkReserved(chunk);
   AVER(arena->reserved >= size);
   arena->reserved -= size;
 }
diff --git a/mps/code/arenacl.c b/mps/code/arenacl.c
index 554dc963c72..5212faf702b 100644
--- a/mps/code/arenacl.c
+++ b/mps/code/arenacl.c
@@ -131,7 +131,8 @@ static Res clientChunkCreate(Chunk *chunkReturn, ClientArena clientArena,
   clChunk = p;  chunk = ClientChunk2Chunk(clChunk);
 
   res = ChunkInit(chunk, arena, alignedBase,
-                  AddrAlignDown(limit, ArenaGrainSize(arena)), boot);
+                  AddrAlignDown(limit, ArenaGrainSize(arena)),
+                  AddrOffset(base, limit), boot);
   if (res != ResOK)
     goto failChunkInit;
 
@@ -222,17 +223,6 @@ static void ClientChunkFinish(Chunk chunk)
 }
 
 
-/* ClientChunkReserved -- return the amount of reserved address space
- * in a client chunk.
- */
-
-static Size ClientChunkReserved(Chunk chunk)
-{
-  AVERT(Chunk, chunk);
-  return ChunkSize(chunk);
-}
-
-
 /* ClientArenaVarargs -- parse obsolete varargs */
 
 static void ClientArenaVarargs(ArgStruct args[MPS_ARGS_MAX], va_list varargs)
@@ -469,7 +459,6 @@ DEFINE_ARENA_CLASS(ClientArenaClass, this)
   this->free = ClientArenaFree;
   this->chunkInit = ClientChunkInit;
   this->chunkFinish = ClientChunkFinish;
-  this->chunkReserved = ClientChunkReserved;
   AVERT(ArenaClass, this);
 }
 
diff --git a/mps/code/arenavm.c b/mps/code/arenavm.c
index fe1f0f91e9a..b37e7125fdd 100644
--- a/mps/code/arenavm.c
+++ b/mps/code/arenavm.c
@@ -323,7 +323,8 @@ static Res VMChunkCreate(Chunk *chunkReturn, VMArena vmArena, Size size)
 
   /* Copy VM descriptor into its place in the chunk. */
   VMCopy(VMChunkVM(vmChunk), vm);
-  res = ChunkInit(VMChunk2Chunk(vmChunk), arena, base, limit, boot);
+  res = ChunkInit(VMChunk2Chunk(vmChunk), arena, base, limit,
+                  VMReserved(VMChunkVM(vmChunk)), boot);
   if (res != ResOK)
     goto failChunkInit;
 
@@ -456,17 +457,6 @@ static void VMChunkFinish(Chunk chunk)
 }
 
 
-/* VMChunkReserved -- return the amount of reserved address space in a
- * VM chunk.
- */
-
-static Size VMChunkReserved(Chunk chunk)
-{
-  AVERT(Chunk, chunk);
-  return VMReserved(VMChunkVM(Chunk2VMChunk(chunk)));
-}
-
-
 /* VMArenaVarargs -- parse obsolete varargs */
 
 static void VMArenaVarargs(ArgStruct args[MPS_ARGS_MAX], va_list varargs)
@@ -1198,7 +1188,6 @@ DEFINE_ARENA_CLASS(VMArenaClass, this)
   this->free = VMFree;
   this->chunkInit = VMChunkInit;
   this->chunkFinish = VMChunkFinish;
-  this->chunkReserved = VMChunkReserved;
   this->compact = VMCompact;
   this->describe = VMArenaDescribe;
   this->pagesMarkAllocated = VMPagesMarkAllocated;
diff --git a/mps/code/mpmst.h b/mps/code/mpmst.h
index 96e8599e424..fecd90afa54 100644
--- a/mps/code/mpmst.h
+++ b/mps/code/mpmst.h
@@ -536,7 +536,6 @@ typedef struct mps_arena_class_s {
   ArenaFreeMethod free;
   ArenaChunkInitMethod chunkInit;
   ArenaChunkFinishMethod chunkFinish;
-  ArenaChunkReservedMethod chunkReserved;
   ArenaCompactMethod compact;
   ArenaDescribeMethod describe;
   ArenaPagesMarkAllocatedMethod pagesMarkAllocated;
diff --git a/mps/code/mpmtypes.h b/mps/code/mpmtypes.h
index de98355342a..b0d1fe2003a 100644
--- a/mps/code/mpmtypes.h
+++ b/mps/code/mpmtypes.h
@@ -125,7 +125,6 @@ typedef Res (*ArenaExtendMethod)(Arena arena, Addr base, Size size);
 typedef Res (*ArenaGrowMethod)(Arena arena, LocusPref pref, Size size);
 typedef void (*ArenaFreeMethod)(Addr base, Size size, Pool pool);
 typedef Res (*ArenaChunkInitMethod)(Chunk chunk, BootBlock boot);
-typedef Size (*ArenaChunkReservedMethod)(Chunk chunk);
 typedef void (*ArenaChunkFinishMethod)(Chunk chunk);
 typedef void (*ArenaCompactMethod)(Arena arena, Trace trace);
 typedef Res (*ArenaDescribeMethod)(Arena arena, mps_lib_FILE *stream, Count depth);
diff --git a/mps/code/tract.c b/mps/code/tract.c
index 39f6bead95e..9aa815f47ba 100644
--- a/mps/code/tract.c
+++ b/mps/code/tract.c
@@ -167,7 +167,8 @@ Bool ChunkCheck(Chunk chunk)
 
 /* ChunkInit -- initialize generic part of chunk */
 
-Res ChunkInit(Chunk chunk, Arena arena, Addr base, Addr limit, BootBlock boot)
+Res ChunkInit(Chunk chunk, Arena arena, Addr base, Addr limit, Size reserved,
+              BootBlock boot)
 {
   Size size;
   Count pages;
@@ -192,6 +193,7 @@ Res ChunkInit(Chunk chunk, Arena arena, Addr base, Addr limit, BootBlock boot)
   chunk->pageShift = pageShift = SizeLog2(chunk->pageSize);
   chunk->base = base;
   chunk->limit = limit;
+  chunk->reserved = reserved;
   size = ChunkSize(chunk);
 
   chunk->pages = pages = size >> pageShift;
diff --git a/mps/code/tract.h b/mps/code/tract.h
index 07906ad5756..ce7c602a176 100644
--- a/mps/code/tract.h
+++ b/mps/code/tract.h
@@ -148,6 +148,9 @@ typedef struct ChunkStruct {
   BT allocTable;        /* page allocation table */
   Page pageTable;       /* the page table */
   Count pageTablePages; /* number of pages occupied by page table */
+  Size reserved;        /* reserved address space for chunk (including overhead
+                           such as losses due to alignment): must not change
+                           (or arena reserved calculation will break) */
 } ChunkStruct;
 
 
@@ -159,10 +162,11 @@ typedef struct ChunkStruct {
 #define ChunkSizeToPages(chunk, size) ((Count)((size) >> (chunk)->pageShift))
 #define ChunkPage(chunk, pi) (&(chunk)->pageTable[pi])
 #define ChunkOfTree(tree) PARENT(ChunkStruct, chunkTree, tree)
+#define ChunkReserved(chunk) RVALUE((chunk)->reserved)
 
 extern Bool ChunkCheck(Chunk chunk);
 extern Res ChunkInit(Chunk chunk, Arena arena, Addr base, Addr limit,
-                     BootBlock boot);
+                     Size reserved, BootBlock boot);
 extern void ChunkFinish(Chunk chunk);
 extern Compare ChunkCompare(Tree tree, TreeKey key);
 extern TreeKey ChunkKey(Tree tree);