diff --git a/Code/BasicFilters/otbUnaryFunctorObjectListFilter.txx b/Code/BasicFilters/otbUnaryFunctorObjectListFilter.txx
index f3121946697b29dc49a6bbe7c4e8262d20181802..0bccd2a3c7c062593a925b98bb831c63f23a1041 100644
--- a/Code/BasicFilters/otbUnaryFunctorObjectListFilter.txx
+++ b/Code/BasicFilters/otbUnaryFunctorObjectListFilter.txx
@@ -74,7 +74,7 @@ template <class TInputList, class TOutputList, class TFunction  >
 {
   // copy the lists to the output
   OutputListPointer outputPtr = this->GetOutput();
-  for (int i=0; i< this->m_ObjectListPerThread.size(); ++i)
+  for (unsigned int i=0; i< this->m_ObjectListPerThread.size(); ++i)
   {
     for(OutputListIterator it = this->m_ObjectListPerThread[i]->Begin();
         it != this->m_ObjectListPerThread[i]->End();