diff --git a/src/ast/rewriter/arith_rewriter.cpp b/src/ast/rewriter/arith_rewriter.cpp
index 1b52e335dbc..35b45295fde 100644
--- a/src/ast/rewriter/arith_rewriter.cpp
+++ b/src/ast/rewriter/arith_rewriter.cpp
@@ -729,7 +729,9 @@ bool arith_rewriter::mk_eq_mod(expr* arg1, expr* arg2, expr_ref& result) {
 expr_ref arith_rewriter::neg_monomial(expr* e) const {
     expr_ref_vector args(m());
     rational a1;
-    if (is_app(e) && m_util.is_mul(e)) {
+    if (m_util.is_numeral(e, a1)) 
+        args.push_back(m_util.mk_numeral(-a1, e->get_sort()));
+    else if (is_app(e) && m_util.is_mul(e)) {
         if (is_numeral(to_app(e)->get_arg(0), a1)) {
             if (!a1.is_minus_one()) {
                 args.push_back(m_util.mk_numeral(-a1, m_util.is_int(e)));