diff --git a/contracts/Contributors.sol b/contracts/Contributors.sol
index 8bfd872..dd2e61b 100644
--- a/contracts/Contributors.sol
+++ b/contracts/Contributors.sol
@@ -26,7 +26,7 @@ contract Contributors is Upgradeable {
   function initialize(address sender) public payable {
     require(msg.sender == address(registry));
     uint _id = 1;
-    Contributor c = contributors[_id];
+    Contributor storage c = contributors[_id];
     c.exists = true;
     c.isCore = true;
     c.account = sender;
@@ -34,7 +34,7 @@ contract Contributors is Upgradeable {
     contributorsCount += 1;
   }
 
-  function coreContributorsCount() constant public returns (uint) {
+  function coreContributorsCount() view public returns (uint) {
     uint count = 0;
     for (uint256 i = 1; i <= contributorsCount; i++) {
       if (contributors[i].isCore) {
@@ -52,7 +52,7 @@ contract Contributors is Upgradeable {
   }
 
   function updateContributorProfileHash(uint _id, uint8 _hashFunction, uint8 _hashSize, bytes32 _profileHash) public onlyRegistryContractFor('Operator') {
-    Contributor c = contributors[_id];
+    Contributor storage c = contributors[_id];
     bytes32 _oldProfileHash = c.profileHash;
     c.profileHash = _profileHash;
     c.hashFunction = _hashFunction;
@@ -64,7 +64,7 @@ contract Contributors is Upgradeable {
   function addContributor(address _address, uint8 _hashFunction, uint8 _hashSize, bytes32 _profileHash, bool isCore) public onlyRegistryContractFor('Operator') {
     uint _id = contributorsCount + 1;
     if (contributors[_id].exists != true) {
-      Contributor c = contributors[_id];
+      Contributor storage c = contributors[_id];
       c.exists = true;
       c.isCore = isCore;
       c.hashFunction = _hashFunction;
@@ -79,27 +79,27 @@ contract Contributors is Upgradeable {
     }
   }
 
-  function isCore(uint _id) constant public returns (bool) {
+  function isCore(uint _id) view public returns (bool) {
     return contributors[_id].isCore;
   }
 
-  function exists(uint _id) constant public returns (bool) {
+  function exists(uint _id) view public returns (bool) {
     return contributors[_id].exists;
   }
 
-  function addressIsCore(address _address) constant public returns (bool) {
+  function addressIsCore(address _address) view public returns (bool) {
     return getContributorByAddress(_address).isCore;
   }
 
-  function addressExists(address _address) constant public returns (bool) {
+  function addressExists(address _address) view public returns (bool) {
     return getContributorByAddress(_address).exists;
   }
 
-  function getContributorIdByAddress(address _address) constant public returns (uint) {
+  function getContributorIdByAddress(address _address) view public returns (uint) {
     return contributorIds[_address];
   }
 
-  function getContributorAddressById(uint _id) constant public returns (address) {
+  function getContributorAddressById(uint _id) view public returns (address) {
     return contributors[_id].account;
   }
 
diff --git a/contracts/Operator.sol b/contracts/Operator.sol
index 174a062..0bbf9c1 100644
--- a/contracts/Operator.sol
+++ b/contracts/Operator.sol
@@ -46,10 +46,10 @@ contract Operator is Upgradeable {
     return Token(registry.getProxyFor('Token'));
   }
 
-  function contributorsCount() constant public returns (uint) {
+  function contributorsCount() view public returns (uint) {
     return contributorsContract().contributorsCount();
   }
-  function coreContributorsCount() constant public returns (uint) {
+  function coreContributorsCount() view public returns (uint) {
     return contributorsContract().coreContributorsCount();
   }
 
@@ -61,15 +61,15 @@ contract Operator is Upgradeable {
     contributorsContract().updateContributorProfileHash(_id, _hashFunction, _hashSize, _profileHash);
   }
 
-  function getContributor(uint _id) constant public returns (address account, uint8 hashFunction, uint8 hashSize, bytes32 profileHash, bool isCore) {
+  function getContributor(uint _id) view public returns (address account, uint8 hashFunction, uint8 hashSize, bytes32 profileHash, bool isCore) {
     bool exists;
 
     (account, profileHash, hashFunction, hashSize, isCore, exists) = contributorsContract().contributors(_id);
 
-    if (!exists) { throw; }
+    require(exists);
   }
 
-  function proposalsCount() constant public returns (uint) {
+  function proposalsCount() view public returns (uint) {
     return proposals.length;
   }
 
@@ -97,8 +97,8 @@ contract Operator is Upgradeable {
 
   function vote(uint256 _proposalId) public coreOnly returns (uint _pId, bool _executed) {
     var p = proposals[_proposalId];
-    if (p.executed) { throw; }
-    if (p.votes[msg.sender] == true) { throw; }
+    require(!p.executed);
+    require(p.votes[msg.sender] != true);
     p.votes[msg.sender] = true;
     p.votesCount++;
     _executed = false;
@@ -110,15 +110,15 @@ contract Operator is Upgradeable {
     ProposalVoted(_pId, msg.sender, p.votesCount);
   }
 
-  function hasVotedFor(address _sender, uint256 _proposalId) public constant returns (bool) {
-    Proposal p = proposals[_proposalId];
+  function hasVotedFor(address _sender, uint256 _proposalId) public view returns (bool) {
+    Proposal storage p = proposals[_proposalId];
     return p.exists && p.votes[_sender];
   }
 
   function executeProposal(uint proposalId) private returns (bool) {
     var p = proposals[proposalId];
-    if (p.executed) { throw; }
-    if (p.votesCount < p.votesNeeded) { throw; }
+    require(!p.executed);
+    require(p.votesCount >= p.votesNeeded);
     address recipientAddress = contributorsContract().getContributorAddressById(p.recipientId);
     tokenContract().mintFor(recipientAddress, p.amount, proposalId);
     p.executed = true;