diff --git a/moo/lib/Makefile.am b/moo/lib/Makefile.am
index 26fbaee..2de7abc 100644
--- a/moo/lib/Makefile.am
+++ b/moo/lib/Makefile.am
@@ -41,6 +41,7 @@ pkginclude_HEADERS = \
 	moo-opt.h \
 	moo-rbt.h \
 	moo-utl.h \
+	moo-xma.h \
 	moo-std.h
 
 ##################################################
@@ -61,7 +62,6 @@ libmoo_la_SOURCES = \
 	moo-rbt.h \
 	moo-utl.h \
 	moo-prv.h \
-	moo-xma.h \
 	pack1.h \
 	unpack.h \
 	bigint.c \
diff --git a/moo/lib/Makefile.in b/moo/lib/Makefile.in
index 0433c4a..7424243 100644
--- a/moo/lib/Makefile.in
+++ b/moo/lib/Makefile.in
@@ -440,6 +440,7 @@ pkginclude_HEADERS = \
 	moo-opt.h \
 	moo-rbt.h \
 	moo-utl.h \
+	moo-xma.h \
 	moo-std.h
 
 pkglib_LTLIBRARIES = libmoo.la libmoox.la
@@ -456,7 +457,6 @@ libmoo_la_SOURCES = \
 	moo-rbt.h \
 	moo-utl.h \
 	moo-prv.h \
-	moo-xma.h \
 	pack1.h \
 	unpack.h \
 	bigint.c \
diff --git a/moo/lib/moo-xma.h b/moo/lib/moo-xma.h
index 0cd3d40..a2107e2 100644
--- a/moo/lib/moo-xma.h
+++ b/moo/lib/moo-xma.h
@@ -91,6 +91,7 @@ struct moo_xma_t
 
 	moo_uint8_t* start; /* zone beginning */
 	moo_uint8_t* end; /* zone end */
+	int          external;
 
 	/** pointer array to free memory blocks */
 	moo_xma_fblk_t* xfree[MOO_XMA_FIXED + MOO_XMA_SIZE_BITS + 1]; 
@@ -134,8 +135,9 @@ extern "C" {
  */
 MOO_EXPORT moo_xma_t* moo_xma_open (
 	moo_mmgr_t* mmgr,    /**< memory manager */
-	moo_oow_t  xtnsize, /**< extension size in bytes */
-	moo_oow_t  zonesize /**< zone size in bytes */
+	moo_oow_t   xtnsize, /**< extension size in bytes */
+	void*       zoneptr,
+	moo_oow_t   zonesize /**< zone size in bytes */
 );
 
 /**
@@ -171,7 +173,8 @@ static MOO_INLINE void* moo_xma_getxtn (moo_xma_t* xma) { return (void*)(xma + 1
 MOO_EXPORT int moo_xma_init (
 	moo_xma_t*  xma,     /**< memory allocator */
 	moo_mmgr_t* mmgr,    /**< memory manager */
-	moo_oow_t  zonesize /**< zone size in bytes */
+	void*       zoneptr,  /**< pointer to memory zone. if #MOO_NULL, a zone is auto-created */
+	moo_oow_t   zonesize /**< zone size in bytes */
 );
 
 /**
diff --git a/moo/lib/xma.c b/moo/lib/xma.c
index e892433..8592d1f 100644
--- a/moo/lib/xma.c
+++ b/moo/lib/xma.c
@@ -125,14 +125,14 @@ static MOO_INLINE moo_oow_t getxfi (moo_xma_t* xma, moo_oow_t size)
 	return xfi;
 }
 
-moo_xma_t* moo_xma_open (moo_mmgr_t* mmgr, moo_oow_t xtnsize, moo_oow_t zonesize)
+moo_xma_t* moo_xma_open (moo_mmgr_t* mmgr, moo_oow_t xtnsize, void* zoneptr, moo_oow_t zonesize)
 {
 	moo_xma_t* xma;
 
 	xma = (moo_xma_t*)MOO_MMGR_ALLOC(mmgr, MOO_SIZEOF(*xma) + xtnsize);
 	if (MOO_UNLIKELY(!xma)) return MOO_NULL;
 
-	if (moo_xma_init(xma, mmgr, zonesize) <= -1)
+	if (moo_xma_init(xma, mmgr, zoneptr, zonesize) <= -1)
 	{
 		MOO_MMGR_FREE (mmgr, xma);
 		return MOO_NULL;
@@ -148,20 +148,28 @@ void moo_xma_close (moo_xma_t* xma)
 	MOO_MMGR_FREE (xma->_mmgr, xma);
 }
 
-int moo_xma_init (moo_xma_t* xma, moo_mmgr_t* mmgr, moo_oow_t zonesize)
+int moo_xma_init (moo_xma_t* xma, moo_mmgr_t* mmgr, void* zoneptr, moo_oow_t zonesize)
 {
 	moo_xma_fblk_t* free;
 	moo_oow_t xfi;
 
-	/* round 'zonesize' to be the multiples of ALIGN */
-	zonesize = MOO_ALIGN_POW2(zonesize, ALIGN);
+	if (!zoneptr)
+	{
+		/* round 'zonesize' to be the multiples of ALIGN */
+		zonesize = MOO_ALIGN_POW2(zonesize, ALIGN);
 
-	/* adjust 'zonesize' to be large enough to hold a single smallest block */
-	if (zonesize < MINBLKLEN) zonesize = MINBLKLEN;
+		/* adjust 'zonesize' to be large enough to hold a single smallest block */
+		if (zonesize < MINBLKLEN) zonesize = MINBLKLEN;
 
-	/* allocate a memory chunk to use for actual memory allocation */
-	free = MOO_MMGR_ALLOC(mmgr, zonesize);
-	if (MOO_UNLIKELY(!free)) return -1;
+		zoneptr = MOO_MMGR_ALLOC(mmgr, zonesize);
+		if (MOO_UNLIKELY(!zoneptr)) return -1;
+	}
+	else
+	{
+		xma->external = 1;
+	}
+
+	free = (moo_xma_fblk_t*)zoneptr;
 
 	/* initialize the header part of the free chunk. the entire zone is a single free block */
 	free->prev_size = 0;
@@ -201,7 +209,7 @@ void moo_xma_fini (moo_xma_t* xma)
 {
 	/* the head must point to the free chunk allocated in init().
 	 * let's deallocate it */
-	MOO_MMGR_FREE (xma->_mmgr, xma->start);
+	if (!xma->external) MOO_MMGR_FREE (xma->_mmgr, xma->start);
 	xma->start = MOO_NULL;
 	xma->end = MOO_NULL;
 }
@@ -650,7 +658,7 @@ void moo_xma_free (moo_xma_t* xma, void* b)
 		/* attach blk to the free list */
 		attach_to_freelist (xma, (moo_xma_fblk_t*)blk);
 	}
-	else if ((moo_uint8_t*)x < xma->end && x->avail)
+	else if ((moo_uint8_t*)x >= xma->start && x->avail)
 	{
 		/*
 		 * Merge the block with the previous block 
@@ -661,17 +669,12 @@ void moo_xma_free (moo_xma_t* xma, void* b)
 		 * +------------+------------+------------+
 		 * |     X      |            |     Y      |
 		 * +------------+------------+------------+
-		 *         ^      |      ^      | 
-		 *         +------+      +------+   
 		 *
-		 *               
-		 *          +---------------------+  
-		 *          |                     v  
 		 * +-------------------------+------------+
 		 * |     X                   |     Y      |
 		 * +-------------------------+------------+
-		 *         ^                    | 
-		 *         +--------------------+   
+		 *
+		 *
 		 *
 		 */
 #if defined(MOO_XMA_ENABLE_STAT)
diff --git a/moo/t/t-005.c b/moo/t/t-005.c
index 7805ede..37d2b26 100644
--- a/moo/t/t-005.c
+++ b/moo/t/t-005.c
@@ -41,7 +41,7 @@ int main ()
 	void* ptr1, * ptr2, * ptr3;
 
 
-	xma = moo_xma_open(&sys_mmgr, 0, 100000);
+	xma = moo_xma_open(&sys_mmgr, 0, MOO_NULL, 100000);
 
 
 	ptr1 = moo_xma_alloc(xma, 1000);