diff --git a/Code/Learning/otbConfusionMatrixCalculator.txx b/Code/Learning/otbConfusionMatrixCalculator.txx
index c46a533a877a92fd38fe0d379aae55eda3e64aff..074de0ff87b399bc9ee479cbaa0e0ba8689c2fb8 100644
--- a/Code/Learning/otbConfusionMatrixCalculator.txx
+++ b/Code/Learning/otbConfusionMatrixCalculator.txx
@@ -101,7 +101,7 @@ ConfusionMatrixCalculator<TRefListLabel, TProdListLabel>
     int prodPos = m_MapOfClasses[prodLabel];
 
     ++samplesPerClass[refPos];
-    m_ConfusionMatrix(refPos, prodPos) += 1;
+    m_ConfusionMatrix(prodPos, refPos) += 1;
 
     ++refIterator;
     ++prodIterator;