diff --git a/include/helpers.hpp b/include/helpers.hpp
index 815693f..85b4742 100644
--- a/include/helpers.hpp
+++ b/include/helpers.hpp
@@ -40,7 +40,7 @@ using std::string;
  *
  *  @since  0.4.0
  */
-const string unescape_html(string html);
+string unescape_html(string html);
 
 } // namespace mastodonpp
 
diff --git a/src/helpers.cpp b/src/helpers.cpp
index 70fdf7d..1add56d 100644
--- a/src/helpers.cpp
+++ b/src/helpers.cpp
@@ -37,7 +37,7 @@ using std::string_view;
 using std::move;
 using std::pair;
 
-const string unescape_html(string html)
+string unescape_html(string html)
 {
     string buffer{move(html)};
     string output;