diff --git a/thin-provisioning/device_tree.h b/thin-provisioning/device_tree.h
index ef32b45..ec0f9f2 100644
--- a/thin-provisioning/device_tree.h
+++ b/thin-provisioning/device_tree.h
@@ -16,12 +16,12 @@ namespace thin_provisioning {
 		} __attribute__ ((packed));
 
 		struct device_details {
+			device_details();
+
 			uint64_t mapped_blocks_;
 			uint64_t transaction_id_;  /* when created */
 			uint32_t creation_time_;
 			uint32_t snapshotted_time_;
-
-			device_details();
 		};
 
 		struct device_details_traits {