diff --git a/iterator.hpp b/iterator.hpp
index ff936a27..62845094 100644
--- a/iterator.hpp
+++ b/iterator.hpp
@@ -301,6 +301,9 @@ namespace util {
         const ContainerT &m_container;
     };
 
+    template <typename ContainerT>
+    indices (ContainerT const&) -> indices<ContainerT>;
+
 
     //-------------------------------------------------------------------------
     template <typename T>