diff --git a/src/mutation_ui.cpp b/src/mutation_ui.cpp
index 0cb6c03d2c71a..d453fffc2e3b8 100644
--- a/src/mutation_ui.cpp
+++ b/src/mutation_ui.cpp
@@ -49,14 +49,14 @@ static const auto shortcut_desc = []( const std::string_view comment, const std:
 
 // needs extensive improvement
 
-static trait_id GetTrait( const std::vector<trait_id> &active,
-                          const std::vector<trait_id> &passive,
-                          int cursor, mutation_tab_mode tab_mode )
+static std::optional<trait_id> GetTrait( const std::vector<trait_id> &active,
+        const std::vector<trait_id> &passive,
+        int cursor, mutation_tab_mode tab_mode )
 {
-    trait_id mut_id;
+    std::optional<trait_id> mut_id;
     if( tab_mode == mutation_tab_mode::active ) {
         mut_id = active[cursor];
-    } else {
+    } else if( tab_mode == mutation_tab_mode::passive ) {
         mut_id = passive[cursor];
     }
     return mut_id;