diff --git a/include/nanobind/nb_cast.h b/include/nanobind/nb_cast.h
index 1aa50ba7..71da158a 100644
--- a/include/nanobind/nb_cast.h
+++ b/include/nanobind/nb_cast.h
@@ -218,6 +218,11 @@ template <> struct type_caster<char> {
 
     static handle from_cpp(const char *value, rv_policy,
                            cleanup_list *) noexcept {
+        if (value == nullptr) {
+            PyObject* result = Py_None;
+            Py_INCREF(result);
+            return result;
+        }
         return PyUnicode_FromString(value);
     }