diff --git a/src/library/simplifier/rewrite_rule_set.cpp b/src/library/simplifier/rewrite_rule_set.cpp
index d0f561585..b29ed8ac2 100644
--- a/src/library/simplifier/rewrite_rule_set.cpp
+++ b/src/library/simplifier/rewrite_rule_set.cpp
@@ -28,7 +28,9 @@ format rewrite_rule::pp(formatter const & fmt) const {
     r += format("#") + format(length(m_metas));
     if (m_is_permutation)
         r += space() + format("perm");
-    r += group(comma() + space() + fmt(m_lhs) + space() + format("↦") + pp_indent_expr(fmt, m_rhs));
+    format r1 = comma() + space() + fmt(m_lhs);
+    r1       += space() + format("↦") + pp_indent_expr(fmt, m_rhs);
+    r += group(r1);
     return r;
 }
 
diff --git a/tests/lean/rw_set3.lean.expected.out b/tests/lean/rw_set3.lean.expected.out
index bcf43ff6e..a5353e9c2 100644
--- a/tests/lean/rw_set3.lean.expected.out
+++ b/tests/lean/rw_set3.lean.expected.out
@@ -1,2 +1,2 @@
 rewrite rules for eq
-#2 perm, nat.add ?M_2 ?M_1 ↦ nat.add ?M_1 ?M_2
+#2 perm, nat.add ?M_1 ?M_2 ↦ nat.add ?M_2 ?M_1