diff --git a/contracts/contracts/DevRewardDistributor.sol b/contracts/contracts/DevRewardDistributor.sol
index 744b15c..d75b31f 100644
--- a/contracts/contracts/DevRewardDistributor.sol
+++ b/contracts/contracts/DevRewardDistributor.sol
@@ -160,6 +160,7 @@ contract DevRewardDistributor {
     }
 
     function transfer(address to, uint256 value) external returns (bool) {
+        require(value > 0, "Value is 0");
         require(lockedBalances[msg.sender].amount == value, "Invalid amount");
         require(block.timestamp > lockedBalances[msg.sender].unlockTime, "Tokens are locked");
 
diff --git a/contracts/test/DevRewardDestributor.spec.ts b/contracts/test/DevRewardDestributor.spec.ts
index 4ed650a..8909eb6 100644
--- a/contracts/test/DevRewardDestributor.spec.ts
+++ b/contracts/test/DevRewardDestributor.spec.ts
@@ -181,6 +181,8 @@ describe("DevRewardDistributor", () => {
   it("claim reward", async () => {
     let lastId = -1;
     for (let i = 0; i < 2; i++) {
+      const initTotalSupply = await rewardDistributor.totalSupply();
+
       const info = getRandomAccountInfo(lastId);
       lastId = info.accountId;
 
@@ -220,6 +222,10 @@ describe("DevRewardDistributor", () => {
       );
 
       expect(await rewardDistributor.isClaimed(info.accountId)).to.be.true;
+
+      expect(await rewardDistributor.totalSupply()).to.eq(
+        initTotalSupply.add(reward)
+      );
     }
   });
 
@@ -254,11 +260,16 @@ describe("DevRewardDistributor", () => {
 
     await ethers.provider.send("evm_increaseTime", [unlockTime.toNumber()]);
 
+    const totalSupply = await rewardDistributor.totalSupply();
     const transferTx = await rewardDistributor.transfer(
       developerAccount.address,
       reward
     );
 
+    expect(await rewardDistributor.totalSupply()).to.eq(
+      totalSupply.sub(reward)
+    );
+
     await expect(transferTx)
       .to.emit(token, "Transfer")
       .withArgs(rewardDistributor.address, developerAccount.address, reward);