diff --git a/persistent-data/block.h b/persistent-data/block.h
index 1af46ba..a39da3d 100644
--- a/persistent-data/block.h
+++ b/persistent-data/block.h
@@ -198,6 +198,11 @@ namespace persistent_data {
 
 		void flush() const;
 
+
+		// This is just for unit tests, don't call in application
+		// code.
+		bool is_locked(block_address b) const;
+
 	private:
 		void check(block_address b) const;
 		void write_block(typename block::ptr b) const;
diff --git a/persistent-data/block.tcc b/persistent-data/block.tcc
index 28c87dc..1ffb0c7 100644
--- a/persistent-data/block.tcc
+++ b/persistent-data/block.tcc
@@ -527,4 +527,11 @@ block_manager<BlockSize>::flush() const
 		boost::bind(&block_manager<BlockSize>::write_block, this, _1));
 }
 
+template <uint32_t BlockSize>
+bool
+block_manager<BlockSize>::is_locked(block_address b) const
+{
+	return tracker_.is_locked(b);
+}
+
 //----------------------------------------------------------------
diff --git a/persistent-data/lock_tracker.cc b/persistent-data/lock_tracker.cc
index eac9752..b7800c3 100644
--- a/persistent-data/lock_tracker.cc
+++ b/persistent-data/lock_tracker.cc
@@ -116,5 +116,12 @@ lock_tracker::check_key(uint64_t key) const
 		throw runtime_error("invalid key");
 }
 
+bool
+lock_tracker::is_locked(uint64_t key) const
+{
+	check_key(key);
+	return found(locks_.find(key));
+}
+
 //----------------------------------------------------------------
 
diff --git a/persistent-data/lock_tracker.h b/persistent-data/lock_tracker.h
index f54ad42..497e2cd 100644
--- a/persistent-data/lock_tracker.h
+++ b/persistent-data/lock_tracker.h
@@ -37,6 +37,8 @@ namespace persistent_data {
 		void superblock_lock(uint64_t key);
 		void unlock(uint64_t key);
 
+		bool is_locked(uint64_t key) const;
+
 	private:
 		typedef std::map<uint64_t, int> LockMap;