diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 1561abf3363..f8d282bbbb6 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -210,6 +210,25 @@ struct Some {
 }
 ```
 
+#### For-loop
+The variable in the for-loop shall not be initialized with 0, and we enforce using `++var` instead of `var++``.
+
+This is **correct**:
+
+```
+for (uint256 i; i < 100; ++i) {
+}
+
+```
+
+This is **wrong**:
+
+```
+for (uint256 i = 0; i < 100; i++) {
+}
+
+```
+
 #### Mentioning other files in the repo
 
 To mention another contract file in the repo use the standard like this:
diff --git a/packages/protocol/contracts/L1/provers/Guardians.sol b/packages/protocol/contracts/L1/provers/Guardians.sol
index a4daa55379e..d84a5fbac86 100644
--- a/packages/protocol/contracts/L1/provers/Guardians.sol
+++ b/packages/protocol/contracts/L1/provers/Guardians.sol
@@ -77,7 +77,7 @@ abstract contract Guardians is EssentialContract {
         delete guardians;
 
         // Set the new guardians
-        for (uint256 i = 0; i < _newGuardians.length; ++i) {
+        for (uint256 i; i < _newGuardians.length; ++i) {
             address guardian = _newGuardians[i];
             if (guardian == address(0)) revert INVALID_GUARDIAN();
             // This makes sure there are not duplicate addresses