diff --git a/man/overview.doc b/man/overview.doc
index 78fd808627..7157786e11 100644
--- a/man/overview.doc
+++ b/man/overview.doc
@@ -2174,6 +2174,11 @@ following \verb$~$ (tilde) sequences are replaced:
 \end{tabular}
 \end{center}
 
+    \prologflagitem{toplevel_residue_vars}{bool}{rw}
+When \const{true} (default \const{false}), print residual variables as
+detected by call_residue_vars/2 that do not appear in the bindings
+returned by the goal.
+
     \prologflagitem{toplevel_var_size}{int}{rw}
 Maximum size counted in literals of a term returned as a binding for a
 variable in a top-level query that is saved for re-use using the