diff --git a/contracts/xBitsToken.sol b/contracts/xBitsToken.sol
index a0e42e6..8fb38ac 100644
--- a/contracts/xBitsToken.sol
+++ b/contracts/xBitsToken.sol
@@ -426,9 +426,9 @@ contract xBitsToken is ERC20Standard("xBits","xBits Token",8), EIP2612 {
 
     uint public epochCount; 
 
-    uint public _BLOCKS_PER_READJUSTMENT = 1024;   
-    uint public  _MINIMUM_TARGET = 2**16;      
-    uint public  _MAXIMUM_TARGET = 2**234;
+    uint public constant _BLOCKS_PER_READJUSTMENT = 1024;   
+    uint public constant _MINIMUM_TARGET = 2**16;      
+    uint public constant _MAXIMUM_TARGET = 2**234;
 
 
     uint public miningTarget;