diff --git a/CMakeLists.txt b/CMakeLists.txt
index 155d11e..3a74ff5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.20)
 include(cmake/color.cmake)
-set(BLT_VERSION 5.2.19)
+set(BLT_VERSION 5.2.20)
 
 set(BLT_TARGET BLT)
 
diff --git a/include/blt/parse/argparse_v2.h b/include/blt/parse/argparse_v2.h
index 3ff1fc5..0105bf5 100644
--- a/include/blt/parse/argparse_v2.h
+++ b/include/blt/parse/argparse_v2.h
@@ -394,7 +394,7 @@ namespace blt::argparse
             return std::get<std::string>(m_data.at(key));
         }
 
-        bool contains(const std::string_view key)
+        bool contains(const std::string_view key) const
         {
             return m_data.find(key) != m_data.end();
         }