diff --git a/src/blackmisc/collection.h b/src/blackmisc/collection.h
index ac1d46361..56e095a01 100644
--- a/src/blackmisc/collection.h
+++ b/src/blackmisc/collection.h
@@ -42,7 +42,7 @@ namespace BlackMisc
         typedef typename Iterators::ConstForwardIterator<T> const_iterator;
         typedef const_iterator iterator; // can't modify elements in-place
         typedef ptrdiff_t difference_type;
-        typedef int size_type;
+        typedef intptr_t size_type;
         //! @}
 
         /*!
diff --git a/src/blackmisc/sequence.h b/src/blackmisc/sequence.h
index 8e70ba8dd..2fc318c56 100644
--- a/src/blackmisc/sequence.h
+++ b/src/blackmisc/sequence.h
@@ -42,7 +42,7 @@ namespace BlackMisc
         typedef typename Iterators::ConstBidirectionalIterator<T> const_iterator;
         typedef typename Iterators::BidirectionalIterator<T> iterator;
         typedef ptrdiff_t difference_type;
-        typedef int size_type;
+        typedef intptr_t size_type;
         //! @}
 
         /*!