diff --git a/contracts/crowdsale/Crowdsale.sol b/contracts/crowdsale/Crowdsale.sol
index 32eb1b4dd..26ed8df85 100644
--- a/contracts/crowdsale/Crowdsale.sol
+++ b/contracts/crowdsale/Crowdsale.sol
@@ -44,7 +44,7 @@ contract Crowdsale {
     require(_startTime >= now);
     require(_endTime >= _startTime);
     require(_rate > 0);
-    require(_wallet != 0x0);
+    require(_wallet != address(0));
 
     token = createTokenContract();
     startTime = _startTime;
@@ -67,7 +67,7 @@ contract Crowdsale {
 
   // low level token purchase function
   function buyTokens(address beneficiary) public payable {
-    require(beneficiary != 0x0);
+    require(beneficiary != address(0));
     require(validPurchase());
 
     uint256 weiAmount = msg.value;
diff --git a/contracts/ownership/Claimable.sol b/contracts/ownership/Claimable.sol
index 321b9aa68..299f2c8aa 100644
--- a/contracts/ownership/Claimable.sol
+++ b/contracts/ownership/Claimable.sol
@@ -34,6 +34,6 @@ contract Claimable is Ownable {
   function claimOwnership() onlyPendingOwner public {
     OwnershipTransferred(owner, pendingOwner);
     owner = pendingOwner;
-    pendingOwner = 0x0;
+    pendingOwner = address(0);
   }
 }
diff --git a/contracts/ownership/DelayedClaimable.sol b/contracts/ownership/DelayedClaimable.sol
index 329cd5252..0384b436b 100644
--- a/contracts/ownership/DelayedClaimable.sol
+++ b/contracts/ownership/DelayedClaimable.sol
@@ -35,7 +35,7 @@ contract DelayedClaimable is Claimable {
     require((block.number <= end) && (block.number >= start));
     OwnershipTransferred(owner, pendingOwner);
     owner = pendingOwner;
-    pendingOwner = 0x0;
+    pendingOwner = address(0);
     end = 0;
   }
 
diff --git a/contracts/token/MintableToken.sol b/contracts/token/MintableToken.sol
index 234def478..600d94db5 100644
--- a/contracts/token/MintableToken.sol
+++ b/contracts/token/MintableToken.sol
@@ -35,7 +35,7 @@ contract MintableToken is StandardToken, Ownable {
     totalSupply = totalSupply.add(_amount);
     balances[_to] = balances[_to].add(_amount);
     Mint(_to, _amount);
-    Transfer(0x0, _to, _amount);
+    Transfer(address(0), _to, _amount);
     return true;
   }
 
diff --git a/contracts/token/TokenVesting.sol b/contracts/token/TokenVesting.sol
index da6d4a53f..7d6c87ea0 100644
--- a/contracts/token/TokenVesting.sol
+++ b/contracts/token/TokenVesting.sol
@@ -41,7 +41,7 @@ contract TokenVesting is Ownable {
    * @param _revocable whether the vesting is revocable or not
    */
   function TokenVesting(address _beneficiary, uint256 _start, uint256 _cliff, uint256 _duration, bool _revocable) {
-    require(_beneficiary != 0x0);
+    require(_beneficiary != address(0));
     require(_cliff <= _duration);
 
     beneficiary = _beneficiary;