diff --git a/src/api/z3_optimization.h b/src/api/z3_optimization.h
index 3cdacc46d..889db94ea 100644
--- a/src/api/z3_optimization.h
+++ b/src/api/z3_optimization.h
@@ -82,7 +82,7 @@ extern "C" {
        \param c - context
        \param o - optimization context
        \param a - formula
-       \param weight - a positive weight, penalty for violating soft constraint
+       \param weight - a penalty for violating soft constraint. Negative weights convert into rewards.
        \param id - optional identifier to group soft constraints
 
        \sa Z3_optimize_assert