diff --git a/README.md b/README.md
index c5e90a0fe..f866b881e 100644
--- a/README.md
+++ b/README.md
@@ -125,6 +125,7 @@ Interested in contributing to OpenZeppelin?
 - Framework proposal and roadmap: https://medium.com/zeppelin-blog/zeppelin-framework-proposal-and-development-roadmap-fdfa9a3a32ab#.iain47pak
 - Issue tracker: https://github.com/OpenZeppelin/openzeppelin-solidity/issues
 - Contribution guidelines: https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/CONTRIBUTING.md
+- Code-style guide: https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/CODE_STYLE.md
 - Wiki: https://github.com/OpenZeppelin/openzeppelin-solidity/wiki
 
 ## License
diff --git a/contracts/access/SignatureBouncer.sol b/contracts/access/SignatureBouncer.sol
index 644b34374..9a6092ea6 100644
--- a/contracts/access/SignatureBouncer.sol
+++ b/contracts/access/SignatureBouncer.sol
@@ -33,9 +33,9 @@ contract SignatureBouncer is Ownable, RBAC {
   using ECRecovery for bytes32;
 
   string public constant ROLE_BOUNCER = "bouncer";
-  uint constant METHOD_ID_SIZE = 4;
+  uint internal constant METHOD_ID_SIZE = 4;
   // signature size is 65 bytes (tightly packed v + r + s), but gets padded to 96 bytes
-  uint constant SIGNATURE_SIZE = 96;
+  uint internal constant SIGNATURE_SIZE = 96;
 
   /**
    * @dev requires that a valid signature of a bouncer was provided
diff --git a/contracts/mocks/ERC721ReceiverMock.sol b/contracts/mocks/ERC721ReceiverMock.sol
index cfe73a2e2..a29d0ca2f 100644
--- a/contracts/mocks/ERC721ReceiverMock.sol
+++ b/contracts/mocks/ERC721ReceiverMock.sol
@@ -4,8 +4,8 @@ import "../token/ERC721/IERC721Receiver.sol";
 
 
 contract ERC721ReceiverMock is IERC721Receiver {
-  bytes4 retval_;
-  bool reverts_;
+  bytes4 internal retval_;
+  bool internal reverts_;
 
   event Received(
     address _operator,
diff --git a/contracts/mocks/RBACMock.sol b/contracts/mocks/RBACMock.sol
index 7c2dbf79f..64b174c5b 100644
--- a/contracts/mocks/RBACMock.sol
+++ b/contracts/mocks/RBACMock.sol
@@ -5,7 +5,7 @@ import "../examples/RBACWithAdmin.sol";
 
 contract RBACMock is RBACWithAdmin {
 
-  string constant ROLE_ADVISOR = "advisor";
+  string internal constant ROLE_ADVISOR = "advisor";
 
   modifier onlyAdminOrAdvisor()
   {
diff --git a/contracts/mocks/SafeERC20Helper.sol b/contracts/mocks/SafeERC20Helper.sol
index d64d7c0de..dfc2fb2c0 100644
--- a/contracts/mocks/SafeERC20Helper.sol
+++ b/contracts/mocks/SafeERC20Helper.sol
@@ -61,35 +61,35 @@ contract ERC20SucceedingMock is IERC20 {
 contract SafeERC20Helper {
   using SafeERC20 for IERC20;
 
-  IERC20 failing;
-  IERC20 succeeding;
+  IERC20 internal failing_;
+  IERC20 internal succeeding_;
 
   constructor() public {
-    failing = new ERC20FailingMock();
-    succeeding = new ERC20SucceedingMock();
+    failing_ = new ERC20FailingMock();
+    succeeding_ = new ERC20SucceedingMock();
   }
 
   function doFailingTransfer() public {
-    failing.safeTransfer(address(0), 0);
+    failing_.safeTransfer(address(0), 0);
   }
 
   function doFailingTransferFrom() public {
-    failing.safeTransferFrom(address(0), address(0), 0);
+    failing_.safeTransferFrom(address(0), address(0), 0);
   }
 
   function doFailingApprove() public {
-    failing.safeApprove(address(0), 0);
+    failing_.safeApprove(address(0), 0);
   }
 
   function doSucceedingTransfer() public {
-    succeeding.safeTransfer(address(0), 0);
+    succeeding_.safeTransfer(address(0), 0);
   }
 
   function doSucceedingTransferFrom() public {
-    succeeding.safeTransferFrom(address(0), address(0), 0);
+    succeeding_.safeTransferFrom(address(0), address(0), 0);
   }
 
   function doSucceedingApprove() public {
-    succeeding.safeApprove(address(0), 0);
+    succeeding_.safeApprove(address(0), 0);
   }
 }