diff --git a/contracts/common/Controlled.sol b/contracts/common/Controlled.sol
index d2773f3..7b615b6 100644
--- a/contracts/common/Controlled.sol
+++ b/contracts/common/Controlled.sol
@@ -10,7 +10,7 @@ contract Controlled {
 
     address public controller;
 
-    constructor() public { 
+    constructor() internal { 
         controller = msg.sender; 
     }
 
diff --git a/contracts/common/Owned.sol b/contracts/common/Owned.sol
index 177bf0f..18f03e7 100644
--- a/contracts/common/Owned.sol
+++ b/contracts/common/Owned.sol
@@ -14,7 +14,7 @@ contract Owned {
     address public owner;
 
     /// @notice The Constructor assigns the message sender to be `owner`
-    constructor() public {
+    constructor() internal {
         owner = msg.sender;
     }