diff --git a/thin-provisioning/mapping_tree.cc b/thin-provisioning/mapping_tree.cc
index c1a9358..5b69fe9 100644
--- a/thin-provisioning/mapping_tree.cc
+++ b/thin-provisioning/mapping_tree.cc
@@ -64,7 +64,7 @@ namespace thin_provisioning {
 
 		//--------------------------------
 
-		mtree_ref_counter::mtree_ref_counter(transaction_manager::ptr tm)
+		mtree_ref_counter::mtree_ref_counter(transaction_manager &tm)
 			: tm_(tm)
 		{
 		}
diff --git a/thin-provisioning/mapping_tree.h b/thin-provisioning/mapping_tree.h
index 4e6adda..ce88ba2 100644
--- a/thin-provisioning/mapping_tree.h
+++ b/thin-provisioning/mapping_tree.h
@@ -45,13 +45,13 @@ namespace thin_provisioning {
 
 		class mtree_ref_counter {
 		public:
-			mtree_ref_counter(transaction_manager::ptr tm);
+			mtree_ref_counter(transaction_manager &tm);
 
 			void inc(block_address b);
 			void dec(block_address b);
 
 		private:
-			transaction_manager::ptr tm_;
+			transaction_manager &tm_;
 		};
 
 		// This value type is itself a tree containing mappings.
diff --git a/thin-provisioning/metadata.cc b/thin-provisioning/metadata.cc
index 67c08ae..7f91b51 100644
--- a/thin-provisioning/metadata.cc
+++ b/thin-provisioning/metadata.cc
@@ -71,7 +71,7 @@ metadata::metadata(block_manager<>::ptr bm, open_type ot,
 		details_ = device_tree::ptr(new device_tree(*tm_, sb_.device_details_root_,
 							    device_tree_detail::device_details_traits::ref_counter()));
 		mappings_top_level_ = dev_tree::ptr(new dev_tree(*tm_, sb_.data_mapping_root_,
-								 mapping_tree_detail::mtree_ref_counter(tm_)));
+								 mapping_tree_detail::mtree_ref_counter(*tm_)));
 		mappings_ = mapping_tree::ptr(new mapping_tree(*tm_, sb_.data_mapping_root_,
 							       mapping_tree_detail::block_time_ref_counter(data_sm_)));
 		break;
@@ -89,7 +89,7 @@ metadata::metadata(block_manager<>::ptr bm, open_type ot,
 		mappings_ = mapping_tree::ptr(new mapping_tree(*tm_,
 							       mapping_tree_detail::block_time_ref_counter(data_sm_)));
 		mappings_top_level_ = dev_tree::ptr(new dev_tree(*tm_, mappings_->get_root(),
-								 mapping_tree_detail::mtree_ref_counter(tm_)));
+								 mapping_tree_detail::mtree_ref_counter(*tm_)));
 
 		::memset(&sb_, 0, sizeof(sb_));
 		sb_.magic_ = SUPERBLOCK_MAGIC;
@@ -164,7 +164,7 @@ void metadata::open_btrees()
 	details_ = device_tree::ptr(new device_tree(*tm_, sb_.device_details_root_,
 						    device_tree_detail::device_details_traits::ref_counter()));
 	mappings_top_level_ = dev_tree::ptr(new dev_tree(*tm_, sb_.data_mapping_root_,
-							 mapping_tree_detail::mtree_ref_counter(tm_)));
+							 mapping_tree_detail::mtree_ref_counter(*tm_)));
 	mappings_ = mapping_tree::ptr(new mapping_tree(*tm_, sb_.data_mapping_root_,
 						       mapping_tree_detail::block_time_ref_counter(data_sm_)));
 }
diff --git a/thin-provisioning/thin_check.cc b/thin-provisioning/thin_check.cc
index c553cb7..6373603 100644
--- a/thin-provisioning/thin_check.cc
+++ b/thin-provisioning/thin_check.cc
@@ -253,7 +253,7 @@ namespace {
 			{
 				nested_output::nest _ = out.push();
 				dev_tree dtree(*tm, mapping_root(sb, fs),
-					       mapping_tree_detail::mtree_traits::ref_counter(tm));
+					       mapping_tree_detail::mtree_traits::ref_counter(*tm));
 				check_mapping_tree(dtree, mapping_rep);
 			}
 
diff --git a/thin-provisioning/thin_ll_dump.cc b/thin-provisioning/thin_ll_dump.cc
index bc11cf2..2c63b37 100644
--- a/thin-provisioning/thin_ll_dump.cc
+++ b/thin-provisioning/thin_ll_dump.cc
@@ -215,7 +215,7 @@ namespace {
 		// output the top-level data mapping tree
 		ll_mapping_tree_emitter ll_mte(tm->get_bm(), out);
 		dev_tree dtree(*tm, sb.data_mapping_root_,
-			       mapping_tree_detail::mtree_traits::ref_counter(tm));
+			       mapping_tree_detail::mtree_traits::ref_counter(*tm));
 		noop_damage_visitor noop_dv;
 		btree_visit_values(dtree, ll_mte, noop_dv);