diff --git a/thin-provisioning/device_checker.cc b/thin-provisioning/device_checker.cc
index 6521f95..dcca01b 100644
--- a/thin-provisioning/device_checker.cc
+++ b/thin-provisioning/device_checker.cc
@@ -5,7 +5,7 @@ using namespace thin_provisioning;
 //----------------------------------------------------------------
 
 device_checker::device_checker(block_manager::ptr bm)
-	: bm_(bm)
+	: checker(bm)
 {
 }
 
diff --git a/thin-provisioning/device_checker.h b/thin-provisioning/device_checker.h
index 413f49e..ff4d561 100644
--- a/thin-provisioning/device_checker.h
+++ b/thin-provisioning/device_checker.h
@@ -10,10 +10,6 @@ namespace thin_provisioning {
 	public:
 		device_checker(block_manager::ptr bm);
 		damage_list_ptr check();
-
-	private:
-		block_manager::ptr bm_;
-		damage_list_ptr damage_;
 	};
 }
 
diff --git a/thin-provisioning/metadata_checker.cc b/thin-provisioning/metadata_checker.cc
index f6badc5..5276a0b 100644
--- a/thin-provisioning/metadata_checker.cc
+++ b/thin-provisioning/metadata_checker.cc
@@ -165,6 +165,13 @@ metadata_damage_visitor::visit(metadata_damage const &damage)
 	damage.visit(*this);
 }
 
+//--------------------------------
+
+checker::checker(block_manager::ptr bm)
+	: bm_(bm)
+{
+}
+
 //----------------------------------------------------------------
 
 #if 0
diff --git a/thin-provisioning/metadata_checker.h b/thin-provisioning/metadata_checker.h
index 4c37e1c..16f5ebb 100644
--- a/thin-provisioning/metadata_checker.h
+++ b/thin-provisioning/metadata_checker.h
@@ -156,8 +156,13 @@ namespace thin_provisioning {
 		typedef persistent_data::block_manager<> block_manager;
 		typedef boost::shared_ptr<checker> ptr;
 
+		checker(block_manager::ptr bm);
+
 		virtual ~checker() {};
 		virtual damage_list_ptr check() = 0;
+
+	protected:
+		block_manager::ptr bm_;
 	};
 }
 
diff --git a/thin-provisioning/superblock_checker.cc b/thin-provisioning/superblock_checker.cc
index 91b6ba1..f2dd625 100644
--- a/thin-provisioning/superblock_checker.cc
+++ b/thin-provisioning/superblock_checker.cc
@@ -9,8 +9,7 @@ using namespace thin_provisioning;
 //----------------------------------------------------------------
 
 superblock_checker::superblock_checker(block_manager::ptr bm)
-	: bm_(bm),
-	  damage(new damage_list)
+	: checker(bm)
 {
 }
 
diff --git a/thin-provisioning/superblock_checker.h b/thin-provisioning/superblock_checker.h
index bf0253b..fd50a5d 100644
--- a/thin-provisioning/superblock_checker.h
+++ b/thin-provisioning/superblock_checker.h
@@ -10,11 +10,6 @@ namespace thin_provisioning {
 	public:
 		superblock_checker(block_manager::ptr bm);
 		damage_list_ptr check();
-
-	private:
-		// FIXME: surely we can push these down to the base class?
-		block_manager::ptr bm_;
-		damage_list_ptr damage;
 	};
 }