diff --git a/lib/blockchain.js b/lib/blockchain.js
index 50b46275..6498491b 100644
--- a/lib/blockchain.js
+++ b/lib/blockchain.js
@@ -63,7 +63,7 @@ BlockChain.prototype.proposeNewBlock = function(block) {
     commonAncestor = pointer;
 
     pointer = this.tip;
-    while (pointer != commonAncestor) {
+    while (pointer !== commonAncestor) {
       toUnconfirm.push(pointer);
       pointer = this.prev[pointer];
     }
@@ -105,9 +105,9 @@ BlockChain.prototype.unconfirm = function(hash) {
 
   this.tip = prevHash;
   var height = this.height[hash];
-  this.next[prevHash] = undefined;
-  this.hashByHeight[height] = undefined;
-  this.height[hash] = undefined;
+  delete this.next[prevHash];
+  delete this.hashByHeight[height];
+  delete this.height[hash];
 };
 
 BlockChain.prototype.getBlockLocator = function() {
@@ -132,6 +132,16 @@ BlockChain.prototype.hasData = function(hash) {
   return !!this.prev[hash];
 };
 
+BlockChain.prototype.prune = function() {
+  var self = this;
+  _.each(this.prev, function(key, value) {
+    if (!self.height[key]) {
+      delete this.prev[key];
+      delete this.work[key];
+    }
+  });
+};
+
 BlockChain.prototype.toObject = function() {
   return {
     tip: this.tip,