Unicorn Incorrect change bug fix

Bug fix in the change calculation for the Unicorn token with natural number 1

contracts/TokenSellerFactory.sol

@@ -9,7 +9,12 @@ pragma solidity ^0.4.4;
 // This caters for the Golem Network Token which does not implement the
 // ERC20 transferFrom(...), approve(...) and allowance(...) methods
 //
-// Enjoy. (c) JonnyLatte, Cintix & BokkyPooBah 2016. The MIT licence.
+// History:
+// Jan 25 2017 - BPB Added makerTransferAsset(...)
+// Feb 05 2017 - BPB Bug fix in the change calculation for the Unicorn
+// token with natural number 1
+//
+// Enjoy. (c) JonnyLatte, Cintix & BokkyPooBah 2017. The MIT licence.
 // ------------------------------------------------------------------------
 
 // https://github.com/ethereum/EIPs/issues/20
@@ -68,7 +73,7 @@ contract TokenSeller is Owned {
  uint256 _sellPrice,
  uint256 _units,
  bool _sellsTokens
- ) internal {
+ ) {
  asset = _asset;
  sellPrice = _sellPrice;
  units = _units;
@@ -178,13 +183,15 @@ contract TokenSeller is Owned {
  // Note that units has already been validated as > 0
  uint can_sell = ERC20Partial(asset).balanceOf(address(this)) / units;
  uint256 change = 0;
- if (order > can_sell) {
- change = msg.value - (can_sell * sellPrice);
+ if (msg.value > (can_sell * sellPrice)) {
+ change  = msg.value - (can_sell * sellPrice);
  order = can_sell;
+ }
+ if (change > 0) {
  if (!msg.sender.send(change)) throw;
  }
  if (order > 0) {
- if(!ERC20Partial(asset).transfer(msg.sender, order * units)) throw;
+ if (!ERC20Partial(asset).transfer(msg.sender, order * units)) throw;
  }
  TakerBoughtAsset(msg.sender, msg.value, change, order * units);
  }

contracts/TokenTraderFactory.sol

@@ -10,7 +10,13 @@ pragma solidity ^0.4.4;
 // directly as the token does not implement the ERC20
 // transferFrom(...), approve(...) and allowance(...) methods
 //
-// Enjoy. (c) JonnyLatte & BokkyPooBah 2016. The MIT licence.
+// History:
+// Jan 25 2017 - BPB Added makerTransferAsset(...) and
+// makerTransferEther(...)
+// Feb 05 2017 - BPB Bug fix in the change calculation for the Unicorn
+// token with natural number 1
+//
+// Enjoy. (c) JonnyLatte & BokkyPooBah 2017. The MIT licence.
 // ------------------------------------------------------------------------
 
 // https://github.com/ethereum/EIPs/issues/20
@@ -82,7 +88,7 @@ contract TokenTrader is Owned {
  uint256 _units,
  bool _buysTokens,
  bool _sellsTokens
- ) internal {
+ ) {
  asset = _asset;
  buyPrice = _buyPrice;
  sellPrice = _sellPrice;
@@ -255,13 +261,15 @@ contract TokenTrader is Owned {
  // Note that units has already been validated as > 0
  uint can_sell = ERC20(asset).balanceOf(address(this)) / units;
  uint256 change = 0;
- if (order > can_sell) {
- change = msg.value - (can_sell * sellPrice);
+ if (msg.value > (can_sell * sellPrice)) {
+ change  = msg.value - (can_sell * sellPrice);
  order = can_sell;
+ }
+ if (change > 0) {
  if (!msg.sender.send(change)) throw;
  }
  if (order > 0) {
- if(!ERC20(asset).transfer(msg.sender, order * units)) throw;
+ if (!ERC20(asset).transfer(msg.sender, order * units)) throw;
  }
  TakerBoughtAsset(msg.sender, msg.value, change, order * units);
  }
@@ -298,9 +306,9 @@ contract TokenTrader is Owned {
  if (order > can_buy) order = can_buy;
  if (order > 0) {
  // Extract user tokens
- if(!ERC20(asset).transferFrom(msg.sender, address(this), order * units)) throw;
+ if (!ERC20(asset).transferFrom(msg.sender, address(this), order * units)) throw;
  // Pay user
- if(!msg.sender.send(order * buyPrice)) throw;
+ if (!msg.sender.send(order * buyPrice)) throw;
  }
  TakerSoldAsset(msg.sender, etherValueOfTokensToSell, order * units, order * buyPrice);
  }