diff --git a/lib/bcoin/chaindb.js b/lib/bcoin/chaindb.js
index 1754bea4..672c6e85 100644
--- a/lib/bcoin/chaindb.js
+++ b/lib/bcoin/chaindb.js
@@ -437,8 +437,7 @@ ChainDB.prototype.addCache = function addCache(entry) {
  */
 
 ChainDB.prototype.hasCache = function hasCache(hash) {
-  if (hash == null || hash < 0)
-    return false;
+  checkHash(hash);
 
   if (typeof hash === 'number')
     return this.cacheHeight.has(hash);
@@ -454,8 +453,7 @@ ChainDB.prototype.hasCache = function hasCache(hash) {
  */
 
 ChainDB.prototype.getCache = function getCache(hash) {
-  if (hash == null || hash < 0)
-    return;
+  checkHash(hash);
 
   if (typeof hash === 'number')
     return this.cacheHeight.get(hash);
@@ -472,10 +470,7 @@ ChainDB.prototype.getCache = function getCache(hash) {
 ChainDB.prototype.getHeight = function getHeight(hash, callback) {
   var entry;
 
-  if (hash == null || hash < 0) {
-    callback = utils.asyncify(callback);
-    return callback(null, -1);
-  }
+  checkHash(hash);
 
   if (typeof hash === 'number') {
     callback = utils.asyncify(callback);
@@ -518,10 +513,7 @@ ChainDB.prototype.getHeight = function getHeight(hash, callback) {
 ChainDB.prototype.getHash = function getHash(height, callback) {
   var entry;
 
-  if (height == null || height < 0) {
-    callback = utils.asyncify(callback);
-    return callback(null, null);
-  }
+  checkHash(height);
 
   if (typeof height === 'string') {
     callback = utils.asyncify(callback);
@@ -567,8 +559,7 @@ ChainDB.prototype.getChainHeight = function getChainHeight(callback) {
 ChainDB.prototype.getBoth = function getBoth(block, callback) {
   var hash, height;
 
-  if (block == null || block < 0)
-    return utils.asyncify(callback)(null, null, -1);
+  checkHash(block);
 
   if (typeof block === 'string')
     hash = block;
@@ -608,8 +599,7 @@ ChainDB.prototype.getEntry = function getEntry(hash, callback) {
   var self = this;
   var entry;
 
-  if (hash == null || hash < 0)
-    return utils.nextTick(callback);
+  checkHash(hash);
 
   this.getHash(hash, function(err, hash) {
     if (err)
@@ -941,8 +931,7 @@ ChainDB.prototype.reset = function reset(block, callback) {
  */
 
 ChainDB.prototype.has = function has(height, callback) {
-  if (height == null || height < 0)
-    return utils.asyncify(callback)(null, false);
+  checkHash(height);
 
   this.getBoth(height, function(err, hash, height) {
     if (err)
@@ -1880,6 +1869,11 @@ function getSize(value) {
   return 80 + value.length;
 }
 
+function checkHash(hash) {
+  assert(typeof hash === 'string' || typeof hash === 'number',
+    'Must pass in height or hash.');
+}
+
 /*
  * Expose
  */