diff --git a/exprtk.hpp b/exprtk.hpp
index 5f8cac1..7f25afe 100644
--- a/exprtk.hpp
+++ b/exprtk.hpp
@@ -20262,7 +20262,7 @@ namespace exprtk
          return settings_;
       }
 
-      inline parser_error::type get_error(const std::size_t& index)
+      inline parser_error::type get_error(const std::size_t& index) const
       {
          if (index < error_list_.size())
             return error_list_[index];