diff --git a/containers.cpp b/containers.cpp
index de66891..474cc26 100644
--- a/containers.cpp
+++ b/containers.cpp
@@ -79,7 +79,8 @@ packToken TokenList::default_constructor(TokenMap scope) {
 
 packToken* TokenList::ListIterator::next() {
   if (i < list->size()) {
-    return &list->at(i++);
+    TokenList_t::size_type idx = TokenList_t::size_type(i++);
+    return &list->at(idx);
   } else {
     i = 0;
     return NULL;
diff --git a/containers.h b/containers.h
index 7b2adf8..499028b 100644
--- a/containers.h
+++ b/containers.h
@@ -166,7 +166,8 @@ struct TokenList : public Container<TokenList_t>, public Iterable {
     if (list().size() <= idx) {
       throw std::out_of_range("List index out of range!");
     }
-    return list()[idx];
+    TokenList_t::size_type i = TokenList_t::size_type(idx);
+    return list()[i];
   }
 
   void push(packToken val) const { list().push_back(val); }