diff --git a/src/DerolasAuction.sol b/src/DerolasAuction.sol
index 301a303..fd588b9 100644
--- a/src/DerolasAuction.sol
+++ b/src/DerolasAuction.sol
@@ -311,6 +311,7 @@ contract DerolasAuction {
         );
 
         require(roundToDonations[curRound][msg.sender] == 0, "Already donated this round");
+        require(getRemainingRoundLength() > 0, "Round has ended");
 
         roundPoints[curRound].totalDonated += msg.value;
         roundToDonations[curRound][msg.sender] = msg.value;
diff --git a/test/DerolasAuction.t.sol b/test/DerolasAuction.t.sol
index b012338..9dba3d3 100644
--- a/test/DerolasAuction.t.sol
+++ b/test/DerolasAuction.t.sol
@@ -408,4 +408,13 @@ contract TestDerolasAuctionContract is Test {
         assertLt(address(c).balance, minimumTradeAmount, "Contract should have less than minimum trade amount in ETH");
         this.testCanEndRound(); // Ensure the round can be ended without failing
     }
+
+    function testCannotDonateAfterRoundEnd() public {
+        // Check that a user cannot donate after the round has ended
+        this.testTopupIncentivesBalance(); // Ensure incentives are topped up
+        // fast-forward to the block after the round length
+        vm.roll(block.number + roundLength + 1);
+        vm.expectRevert("Round has ended");
+        c.donate{value: minimumDonation}(); // Attempt to donate after round end
+    }
 }