diff --git a/src/test/VestedERC20.t.sol b/src/test/VestedERC20.t.sol
index d7d434a..2e70bc5 100644
--- a/src/test/VestedERC20.t.sol
+++ b/src/test/VestedERC20.t.sol
@@ -147,6 +147,9 @@ contract VestedERC20Test is DSTest {
     function testCorrectness_wrapAndClaim_transfer(uint224 underlyingAmount_)
         public
     {
+        // last test assertion will underflow if we don't
+        vm.assume(underlyingAmount_ > 7);
+
         uint256 underlyingAmount = uint256(underlyingAmount_);
 
         // clear wrapped token balance
@@ -171,7 +174,7 @@ contract VestedERC20Test is DSTest {
 
         // go to when 50% of the vest is done
         vm.warp(startTimestamp + 50 days);
-
+        
         // redeem from this
         redeemedUnderlyingAmount = wrappedToken.redeem(address(this));
         assertGe(
diff --git a/src/test/utils/VM.sol b/src/test/utils/VM.sol
index a733a4a..a1211bd 100644
--- a/src/test/utils/VM.sol
+++ b/src/test/utils/VM.sol
@@ -8,4 +8,6 @@ interface VM {
     function expectRevert(bytes calldata) external;
 
     function prank(address sender) external;
+
+    function assume(bool) external;
 }