diff --git a/src/App/Expression.cpp b/src/App/Expression.cpp
index 103076576b..a682d9422a 100644
--- a/src/App/Expression.cpp
+++ b/src/App/Expression.cpp
@@ -1517,7 +1517,7 @@ void OperatorExpression::_toString(std::ostream &s, bool persistent,int) const
         leftOperator = static_cast<OperatorExpression*>(left)->op;
     if (left->priority() < priority()) // Check on operator priority first
         needsParens = true;
-    else if (leftOperator == op) { // Equal priority?
+    else if (leftOperator == op) { // Same operator ?
         if (!isLeftAssociative())
             needsParens = true;
         //else if (!isCommutative())
@@ -1588,14 +1588,14 @@ void OperatorExpression::_toString(std::ostream &s, bool persistent,int) const
         rightOperator = static_cast<OperatorExpression*>(right)->op;
     if (right->priority() < priority()) // Check on operator priority first
         needsParens = true;
-    else if (rightOperator == op) { // Equal priority?
+    else if (rightOperator == op) { // Same operator ?
         if (!isRightAssociative())
             needsParens = true;
         else if (!isCommutative())
             needsParens = true;
     }
-    else if (right->priority() == priority()) {
-        if (!isRightAssociative())
+    else if (right->priority() == priority()) { // Same priority ?
+        if (!isRightAssociative() || rightOperator == MOD)
             needsParens = true;
     }
 
diff --git a/src/Mod/Test/Document.py b/src/Mod/Test/Document.py
index 3cf2eadf28..3fc39730ab 100644
--- a/src/Mod/Test/Document.py
+++ b/src/Mod/Test/Document.py
@@ -1551,6 +1551,7 @@ class DocumentExpressionCases(unittest.TestCase):
     # must not raise a topological error
     self.assertEqual(self.Doc.recompute(), 2)
 
+
   def testIssue4649(self):
       class Cls():
           def __init__(self, obj):