diff --git a/AnyswapV4ERC20.sol b/AnyswapV4ERC20.sol
index a673b3d..c3689a3 100644
--- a/AnyswapV4ERC20.sol
+++ b/AnyswapV4ERC20.sol
@@ -135,7 +135,7 @@ contract AnyswapV4ERC20 is IAnyswapV3ERC20 {
     bool private _vaultOnly;
 
     // configurable delay for timelock functions
-    uint public delay = 2*24*3600;
+    uint public constant delay = 2*24*3600;
 
 
     // set of minters, can be this bridge or other bridges
diff --git a/AnyswapV5ERC20.sol b/AnyswapV5ERC20.sol
index 29b7b9c..a33e931 100644
--- a/AnyswapV5ERC20.sol
+++ b/AnyswapV5ERC20.sol
@@ -135,7 +135,7 @@ contract AnyswapV5ERC20 is IAnyswapV3ERC20 {
     bool private _vaultOnly;
 
     // configurable delay for timelock functions
-    uint public delay = 2*24*3600;
+    uint public constant delay = 2*24*3600;
 
 
     // set of minters, can be this bridge or other bridges