include/boost/stl_interfaces/iterator_interface.hpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/boost/stl_interfaces/iterator_interface.hpp b/include/boost/stl_interfaces/iterator_interface.hpp
index ec1e474..aa424b7 100644
--- a/include/boost/stl_interfaces/iterator_interface.hpp
+++ b/include/boost/stl_interfaces/iterator_interface.hpp
@@ -650,6 +650,8 @@ namespace boost { namespace stl_interfaces { BOOST_STL_INTERFACES_NAMESPACE_V2 {
         // This iterator concept -> category mapping scheme follows the one
         // from zip_transform_view; see
         // https://eel.is/c++draft/range.zip.transform.iterator#1.
+        // Added the additional case
+        // (input_iterator_tag && !forward_iterator_tag) -> input_iterator_tag
 
         template<typename IteratorConcept, typename ReferenceType>
         constexpr auto category_tag()
@@ -670,7 +672,11 @@ namespace boost { namespace stl_interfaces { BOOST_STL_INTERFACES_NAMESPACE_V2 {
                 } else {
                     return std::forward_iterator_tag{};
                 }
-            } else {
+            } else if constexpr(std::is_base_of_v<
+                                    std::input_iterator_tag,
+                                    IteratorConcept>) {
+                return std::input_iterator_tag{};
+            }else {
                 return 0; // int means "no tag"
             }
         }