diff --git a/spot/misc/optionmap.cc b/spot/misc/optionmap.cc
index c092f0fc0..68cee3662 100644
--- a/spot/misc/optionmap.cc
+++ b/spot/misc/optionmap.cc
@@ -182,7 +182,6 @@ namespace spot
   int
   option_map::operator[](const char* option) const
   {
-    unused_.erase(option);
     return get(option);
   }