diff --git a/include/wx/vector.h b/include/wx/vector.h
index e73b1b9514e5..49b0840c9f6a 100644
--- a/include/wx/vector.h
+++ b/include/wx/vector.h
@@ -160,7 +160,7 @@ class wxVector
 
 public:
     typedef size_t size_type;
-    typedef size_t difference_type;
+    typedef ptrdiff_t difference_type;
     typedef T value_type;
     typedef value_type* pointer;
     typedef const value_type* const_pointer;