diff --git a/Code/Mantid/Algorithms/src/ConvertUnits.cpp b/Code/Mantid/Algorithms/src/ConvertUnits.cpp
index ba7493a932672508663b01e423b5062b8cca02b0..5f115060b5b5ae830dc5d863815802007677cc9e 100644
--- a/Code/Mantid/Algorithms/src/ConvertUnits.cpp
+++ b/Code/Mantid/Algorithms/src/ConvertUnits.cpp
@@ -136,7 +136,7 @@ void ConvertUnits::exec()
   }
 
   // If the units conversion has flipped the ascending direction of X, reverse all the vectors
-  if (outputWS->dataX(0).size() && outputWS->dataX(0).front() < outputWS->dataX(0).back())
+  if (outputWS->dataX(0).size() && outputWS->dataX(0).front() > outputWS->dataX(0).back())
   {
     this->reverse(outputWS);
   }