diff --git a/Code/Mantid/Framework/Algorithms/src/FindPeaks.cpp b/Code/Mantid/Framework/Algorithms/src/FindPeaks.cpp
index 77a2d03f78c5..241703349b93 100644
--- a/Code/Mantid/Framework/Algorithms/src/FindPeaks.cpp
+++ b/Code/Mantid/Framework/Algorithms/src/FindPeaks.cpp
@@ -1095,7 +1095,7 @@ namespace Algorithms
     double lowest = height;
 
     // Extreme case
-    if (i_max == vecX.size())
+    if (i_max == vecY.size())
         i_max = i_max - 1;
 
     // Searching