diff --git a/src/system/kernel/cache/block_allocator.cpp b/src/system/kernel/cache/block_allocator.cpp
index 9c3b5c17ed..e4cbc71763 100644
--- a/src/system/kernel/cache/block_allocator.cpp
+++ b/src/system/kernel/cache/block_allocator.cpp
@@ -23,6 +23,30 @@
 #endif
 
 
+class BlockAddressPool {
+	public:
+		BlockAddressPool();
+		~BlockAddressPool();
+
+		status_t InitCheck() const { return fArea >= B_OK ? B_OK : fArea; }
+
+		size_t RangeSize() const { return kBlockRangeSize; }
+		size_t RangeShift() const { return kBlockRangeShift; }
+		addr_t BaseAddress() const { return fBase; }
+
+		addr_t Get();
+		void Put(addr_t address);
+
+	private:
+		benaphore	fLock;
+		area_id		fArea;
+		addr_t		fBase;
+		addr_t		fFirstFree;
+		int32		fNextFree;
+		int32		fFreeList[kBlockAddressSize / kBlockRangeSize];
+};
+
+
 static class BlockAddressPool sBlockAddressPool;
 
 
diff --git a/src/system/kernel/cache/block_cache.cpp b/src/system/kernel/cache/block_cache.cpp
index f96202c815..d989ce812c 100644
--- a/src/system/kernel/cache/block_cache.cpp
+++ b/src/system/kernel/cache/block_cache.cpp
@@ -82,6 +82,9 @@ static void
 delete_transaction(block_cache *cache, cache_transaction *transaction)
 {
 	hash_remove(cache->transaction_hash, transaction);
+	if (cache->last_transaction == transaction)
+		cache->last_transaction = NULL;
+
 	delete transaction;
 }
 
@@ -132,6 +135,7 @@ block_cache::block_cache(int _fd, off_t numBlocks, size_t blockSize)
 	max_blocks(numBlocks),
 	block_size(blockSize),
 	next_transaction_id(1),
+	last_transaction(NULL),
 	transaction_hash(NULL),
 	ranges_hash(NULL),
 	free_ranges(NULL)
@@ -522,6 +526,9 @@ cache_start_transaction(void *_cache)
 {
 	block_cache *cache = (block_cache *)_cache;
 
+	if (cache->last_transaction && cache->last_transaction->open)
+		panic("last transaction (%ld) still open!\n", cache->last_transaction->id);
+
 	cache_transaction *transaction = new cache_transaction;
 	if (transaction == NULL)
 		return B_NO_MEMORY;
@@ -532,6 +539,7 @@ cache_start_transaction(void *_cache)
 	transaction->notification_hook = NULL;
 	transaction->notification_data = NULL;
 	transaction->open = true;
+	cache->last_transaction = transaction;
 
 	TRACE(("cache_transaction_start(): id %ld started\n", transaction->id));
 
diff --git a/src/system/kernel/cache/block_cache_private.h b/src/system/kernel/cache/block_cache_private.h
index bea33bc760..5691311691 100644
--- a/src/system/kernel/cache/block_cache_private.h
+++ b/src/system/kernel/cache/block_cache_private.h
@@ -90,13 +90,13 @@ struct block_range {
 };
 
 struct block_cache {
-
 	hash_table	*hash;
 	benaphore	lock;
 	int			fd;
 	off_t		max_blocks;
 	size_t		block_size;
 	int32		next_transaction_id;
+	cache_transaction *last_transaction;
 	hash_table	*transaction_hash;
 
 	hash_table	*ranges_hash;
@@ -120,29 +120,6 @@ struct block_cache {
 	void *Allocate();
 };
 
-class BlockAddressPool {
-	public:
-		BlockAddressPool();
-		~BlockAddressPool();
-
-		status_t InitCheck() const { return fArea >= B_OK ? B_OK : fArea; }
-
-		size_t RangeSize() const { return kBlockRangeSize; }
-		size_t RangeShift() const { return kBlockRangeShift; }
-		addr_t BaseAddress() const { return fBase; }
-
-		addr_t Get();
-		void Put(addr_t address);
-
-	private:
-		benaphore	fLock;
-		area_id		fArea;
-		addr_t		fBase;
-		addr_t		fFirstFree;
-		int32		fNextFree;
-		int32		fFreeList[kBlockAddressSize / kBlockRangeSize];
-};
-
 
 #ifdef __cplusplus
 extern "C" {