diff --git a/lib/db/lowlevelup.js b/lib/db/lowlevelup.js
index 63ee4373..5e94fc9c 100644
--- a/lib/db/lowlevelup.js
+++ b/lib/db/lowlevelup.js
@@ -85,7 +85,7 @@ LowlevelUp.prototype.destroy = function destroy(callback) {
   assert(!this.loaded);
 
   if (!this.backend.destroy)
-    return utils.nextTick(callback);
+    return utils.asyncify(callback)(new Error('Cannot destroy.'));
 
   this.backend.destroy(this.location, callback);
 };
@@ -225,6 +225,10 @@ LowlevelUp.prototype.getProperty = function getProperty(name) {
 
 LowlevelUp.prototype.approximateSize = function approximateSize(start, end, callback) {
   assert(this.loaded, 'Cannot use database before it is loaded.');
+
+  if (!this.binding.approximateSize)
+    return utils.asyncify(callback)(new Error('Cannot get size.'));
+
   this.binding.approximateSize(start, end, callback);
 };