diff --git a/Code/BasicFilters/otbSpectralAngleDistanceImageFilter.txx b/Code/BasicFilters/otbSpectralAngleDistanceImageFilter.txx
index 184f59ad4b39d826a795267caa6b3fda2a7a96bb..5b9cba88ab24eec21db8754541acd90c88b83db7 100644
--- a/Code/BasicFilters/otbSpectralAngleDistanceImageFilter.txx
+++ b/Code/BasicFilters/otbSpectralAngleDistanceImageFilter.txx
@@ -44,7 +44,7 @@ SpectralAngleDistanceImageFilter<TInputImage,TOutputImage>
 {
   if ( this->GetInput()->GetNumberOfComponentsPerPixel() == 1 )
   {
-    itkExceptionMacro(<<"Not valid input image : mono channel image not supported.");
+    itkExceptionMacro(<<"Not valid input image : mono channel image gives a nul output image.");
   }
 }