diff --git a/include/boost/histogram/axis.hpp b/include/boost/histogram/axis.hpp
index 1abaf5ba..8d986ba8 100644
--- a/include/boost/histogram/axis.hpp
+++ b/include/boost/histogram/axis.hpp
@@ -28,11 +28,6 @@ template <typename Value> struct bin {
   Value value;
 };
 
-template <> struct bin<const std::string &> {
-  int idx;
-  boost::string_ref value;
-};
-
 template <typename Value> struct real_bin {
   int idx;
   Value left, right;
@@ -510,7 +505,7 @@ private:
  */
 class category_axis : public axis_base<false>, boost::operators<category_axis> {
 public:
-  using value_type = const std::string &;
+  using value_type = boost::string_ref;
   using const_iterator = axis_iterator<category_axis>;
 
   template <typename Iterator>
diff --git a/src/python/axis.cpp b/src/python/axis.cpp
index fc15350e..7bdab51a 100644
--- a/src/python/axis.cpp
+++ b/src/python/axis.cpp
@@ -101,6 +101,14 @@ template <typename T> python::object axis_getitem(const T &t, int i) {
   return python::object(t[i]);
 }
 
+template <> python::object axis_getitem(const category_axis &t, int i) {
+  if (i == axis_len(t)) {
+    PyErr_SetString(PyExc_StopIteration, "no more");
+    python::throw_error_already_set();
+  }
+  return python::object(t[i].data());
+}
+
 template <typename T> std::string axis_repr(const T &t) {
   std::ostringstream os;
   os << t;