diff --git a/src/database/select_query.hpp b/src/database/select_query.hpp
index b9fdc06..e372f2e 100644
--- a/src/database/select_query.hpp
+++ b/src/database/select_query.hpp
@@ -135,7 +135,7 @@ struct SelectQuery: public Query
 };
 
 template <typename... T>
-auto select(const Table<T...> table)
+auto select(const Table<T...>& table)
 {
   SelectQuery<T...> query(table.name);
   return query;
diff --git a/src/utils/dirname.cpp b/src/utils/dirname.cpp
index 71c9c38..a304117 100644
--- a/src/utils/dirname.cpp
+++ b/src/utils/dirname.cpp
@@ -2,7 +2,7 @@
 
 namespace utils
 {
-    std::string dirname(const std::string filename)
+    std::string dirname(const std::string& filename)
     {
       if (filename.empty())
         return "./";
diff --git a/src/utils/dirname.hpp b/src/utils/dirname.hpp
index c1df81b..73e1b57 100644
--- a/src/utils/dirname.hpp
+++ b/src/utils/dirname.hpp
@@ -2,5 +2,5 @@
 
 namespace utils
 {
-std::string dirname(const std::string filename);
+std::string dirname(const std::string& filename);
 }