diff --git a/lib/blocks.js b/lib/blocks.js
index c94f331..565965b 100644
--- a/lib/blocks.js
+++ b/lib/blocks.js
@@ -84,6 +84,15 @@ BlockController.prototype.rawBlock = function(req, res, next, blockArg) {
 
 };
 
+BlockController.prototype._normalizePrevHash = function(hash) {
+  // TODO fix bitcore to give back null instead of null hash
+  if (hash !== '0000000000000000000000000000000000000000000000000000000000000000') {
+    return hash;
+  } else {
+    return null;
+  }
+};
+
 BlockController.prototype.transformBlock = function(block, info) {
   var blockObj = block.toObject();
   var transactionIds = blockObj.transactions.map(function(tx) {
@@ -101,7 +110,7 @@ BlockController.prototype.transformBlock = function(block, info) {
     bits: blockObj.header.bits.toString(16),
     difficulty: block.header.getDifficulty(),
     chainwork: info.chainwork,
-    previousblockhash: blockObj.header.prevHash,
+    previousblockhash: this._normalizePrevHash(blockObj.header.prevHash),
     nextblockhash: info.nextblockhash,
     reward: this.getBlockReward(info.height) / 1e8,
     isMainChain: (info.confirmations !== -1),