diff --git a/Code/BasicFilters/otbUnaryFunctorObjectListBooleanFilter.txx b/Code/BasicFilters/otbUnaryFunctorObjectListBooleanFilter.txx
index 3f71cd877e6c7bcf4241bd63e32d8e1b579c9a3e..cfd2b537518097f39bd8fcdd45619d6d0ccf9218 100644
--- a/Code/BasicFilters/otbUnaryFunctorObjectListBooleanFilter.txx
+++ b/Code/BasicFilters/otbUnaryFunctorObjectListBooleanFilter.txx
@@ -45,7 +45,7 @@ UnaryFunctorObjectListBooleanFilter<TInputList,TOutputList,TFunction>
 {
   InputListPointer inputPtr = this->GetInput();
   OutputListPointer outputPtr = this->GetOutput();
-  
+  outputPtr->Clear();//FIXME this should be probably be in a superclass in a method called before GenerateData()
 
   itk::ProgressReporter progress(this, 0, inputPtr->Size());
   
diff --git a/Code/BasicFilters/otbUnaryFunctorObjectListFilter.txx b/Code/BasicFilters/otbUnaryFunctorObjectListFilter.txx
index bf170b54e2e2dbf3af994e72299b2817e91a0e6f..5ed7146da0f683a281c08cab1849fb7ada2e5aac 100644
--- a/Code/BasicFilters/otbUnaryFunctorObjectListFilter.txx
+++ b/Code/BasicFilters/otbUnaryFunctorObjectListFilter.txx
@@ -45,7 +45,7 @@ UnaryFunctorObjectListFilter<TInputList,TOutputList,TFunction>
 {
   InputListPointer inputPtr = this->GetInput();
   OutputListPointer outputPtr = this->GetOutput();
-  
+  outputPtr->Clear();//FIXME this should be probably be in a superclass in a method called before GenerateData()
 
   itk::ProgressReporter progress(this, 0, inputPtr->Size());