diff --git a/Stream_support/include/CGAL/IO/io.h b/Stream_support/include/CGAL/IO/io.h
index e57d4327bac6..d9c2ea7f761a 100644
--- a/Stream_support/include/CGAL/IO/io.h
+++ b/Stream_support/include/CGAL/IO/io.h
@@ -281,7 +281,11 @@ class Input_rep<std::optional<T>>
   Input_rep( std::optional<T>& tt) : t(tt) {}
 
   //! perform the input, calls \c operator\>\> by default.
-  std::istream& operator()( std::istream& is) const { return (is >> t.value()); }
+  std::istream& operator()( std::istream& is) const {
+    T v;
+    if(is >> v) t = v;
+    return is;
+  }
 };
 
 #if CGAL_FORCE_IFORMAT_DOUBLE || \