diff --git a/contracts/transmuter/libraries/LibHelpers.sol b/contracts/transmuter/libraries/LibHelpers.sol
index c737ffc8..b6cbb026 100644
--- a/contracts/transmuter/libraries/LibHelpers.sol
+++ b/contracts/transmuter/libraries/LibHelpers.sol
@@ -73,7 +73,8 @@ library LibHelpers {
     /// @dev The values in the `xArray` must be increasing
     function piecewiseLinear(uint64 x, uint64[] memory xArray, int64[] memory yArray) internal pure returns (int64) {
         uint256 indexLowerBound = findLowerBound(true, xArray, 1, x);
-        if (indexLowerBound == xArray.length - 1) return yArray[xArray.length - 1];
+        if (indexLowerBound == 0 && x < xArray[0]) return yArray[0];
+        else if (indexLowerBound == xArray.length - 1) return yArray[xArray.length - 1];
         return
             yArray[indexLowerBound] +
             ((yArray[indexLowerBound + 1] - yArray[indexLowerBound]) * int64(x - xArray[indexLowerBound])) /