diff --git a/lib/blockchain/coins.js b/lib/blockchain/coins.js
index 4712c701..f129f6ff 100644
--- a/lib/blockchain/coins.js
+++ b/lib/blockchain/coins.js
@@ -304,7 +304,7 @@ Coins.prototype.fromRaw = function fromRaw(data, hash) {
   code = br.readVarint();
   this.coinbase = (code & 1) !== 0;
 
-  // Recalculate number of non-zero bytes.
+  // Recalculate size.
   size = code / 8 | 0;
 
   if ((code & 6) === 0)
@@ -364,7 +364,7 @@ Coins.parseCoin = function parseCoin(data, hash, index) {
   code = br.readVarint();
   coin.coinbase = (code & 1) !== 0;
 
-  // Recalculate number of non-zero bytes.
+  // Recalculate size.
   size = code / 8 | 0;
 
   if ((code & 6) === 0)
@@ -373,12 +373,13 @@ Coins.parseCoin = function parseCoin(data, hash, index) {
   if (index >= 2 + size * 8)
     return;
 
-  // Read spent field.
+  // Setup spent field.
   offset = br.offset;
   br.seek(size);
 
-  for (i = 2; i <= 4; i += 2) {
-    if ((code & i) !== 0) {
+  // Read first two outputs.
+  for (i = 0; i < 2; i++) {
+    if ((code & (2 << i)) !== 0) {
       if (index === 0) {
         decompress.coin(coin, br);
         return coin;
@@ -391,6 +392,7 @@ Coins.parseCoin = function parseCoin(data, hash, index) {
     index -= 1;
   }
 
+  // Read outputs.
   for (i = 0; i < size; i++) {
     ch = br.data[offset++];
     for (j = 0; j < 8; j++) {
diff --git a/lib/blockchain/undocoins.js b/lib/blockchain/undocoins.js
index 98d607ea..8ee754e8 100644
--- a/lib/blockchain/undocoins.js
+++ b/lib/blockchain/undocoins.js
@@ -195,6 +195,8 @@ UndoCoin.prototype.toRaw = function toRaw(writer) {
   var bw = new BufferWriter(writer);
   var height = this.height;
 
+  assert(height !== 0);
+
   if (height === -1)
     height = 0;