diff --git a/contracts/modules/STO/USDTieredSTO.sol b/contracts/modules/STO/USDTieredSTO.sol
index 825df2122..1d7278796 100644
--- a/contracts/modules/STO/USDTieredSTO.sol
+++ b/contracts/modules/STO/USDTieredSTO.sol
@@ -455,7 +455,7 @@ contract USDTieredSTO is USDTieredSTOStorage, ISTO, ReentrancyGuard {
             fundsRaisedUSD = fundsRaisedUSD.add(spentUSD);
         }
 
-        spentValue = DecimalMath.mul(DecimalMath.div(spentUSD, originalUSD), _investmentValue);
+        spentValue = DecimalMath.div(spentUSD, _rate);
     }
 
     /**
@@ -494,7 +494,7 @@ contract USDTieredSTO is USDTieredSTOStorage, ISTO, ReentrancyGuard {
             }
         }
 
-        spentValue = DecimalMath.mul(DecimalMath.div(spentUSD, originalUSD), _investmentValue);
+        spentValue = DecimalMath.div(spentUSD, rate);
     }
 
     function _buyTokensChecks(