diff --git a/pkg/yqlib/operator_assign.go b/pkg/yqlib/operator_assign.go
index ff13547..e9695b4 100644
--- a/pkg/yqlib/operator_assign.go
+++ b/pkg/yqlib/operator_assign.go
@@ -7,7 +7,7 @@ func assignUpdateOperator(d *dataTreeNavigator, context Context, expressionNode
 	}
 	var rhs Context
 	if !expressionNode.Operation.UpdateAssign {
-		rhs, err = d.GetMatchingNodes(context, expressionNode.Rhs)
+		rhs, err = d.GetMatchingNodes(context.ReadOnlyClone(), expressionNode.Rhs)
 	}
 
 	for el := lhs.MatchingNodes.Front(); el != nil; el = el.Next() {
@@ -44,7 +44,7 @@ func assignAttributesOperator(d *dataTreeNavigator, context Context, expressionN
 	for el := lhs.MatchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 
-		rhs, err := d.GetMatchingNodes(context.SingleChildContext(candidate), expressionNode.Rhs)
+		rhs, err := d.GetMatchingNodes(context.SingleReadonlyChildContext(candidate), expressionNode.Rhs)
 
 		if err != nil {
 			return Context{}, err
diff --git a/pkg/yqlib/operator_assign_test.go b/pkg/yqlib/operator_assign_test.go
index 54901f7..e9dd748 100644
--- a/pkg/yqlib/operator_assign_test.go
+++ b/pkg/yqlib/operator_assign_test.go
@@ -12,6 +12,22 @@ var assignOperatorScenarios = []expressionScenario{
 			"D0, P[], ()::a:\n    b: cat\nx: frog\n",
 		},
 	},
+	{
+		skipDoc:    true,
+		document:   "{}",
+		expression: `.a |= .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: null}\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   "{}",
+		expression: `.a = .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: null}\n",
+		},
+	},
 	{
 		description: "Update node to be the child value",
 		document:    `{a: {b: {g: foof}}}`,
diff --git a/pkg/yqlib/operator_style.go b/pkg/yqlib/operator_style.go
index 693f344..2dfd4a5 100644
--- a/pkg/yqlib/operator_style.go
+++ b/pkg/yqlib/operator_style.go
@@ -31,7 +31,7 @@ func assignStyleOperator(d *dataTreeNavigator, context Context, expressionNode *
 	log.Debugf("AssignStyleOperator: %v")
 	var style yaml.Style
 	if !expressionNode.Operation.UpdateAssign {
-		rhs, err := d.GetMatchingNodes(context, expressionNode.Rhs)
+		rhs, err := d.GetMatchingNodes(context.ReadOnlyClone(), expressionNode.Rhs)
 		if err != nil {
 			return Context{}, err
 		}
@@ -54,7 +54,7 @@ func assignStyleOperator(d *dataTreeNavigator, context Context, expressionNode *
 		candidate := el.Value.(*CandidateNode)
 		log.Debugf("Setting style of : %v", candidate.GetKey())
 		if expressionNode.Operation.UpdateAssign {
-			rhs, err := d.GetMatchingNodes(context.SingleChildContext(candidate), expressionNode.Rhs)
+			rhs, err := d.GetMatchingNodes(context.SingleReadonlyChildContext(candidate), expressionNode.Rhs)
 			if err != nil {
 				return Context{}, err
 			}
diff --git a/pkg/yqlib/operator_tag.go b/pkg/yqlib/operator_tag.go
index 6065350..e447a2f 100644
--- a/pkg/yqlib/operator_tag.go
+++ b/pkg/yqlib/operator_tag.go
@@ -12,7 +12,7 @@ func assignTagOperator(d *dataTreeNavigator, context Context, expressionNode *Ex
 	tag := ""
 
 	if !expressionNode.Operation.UpdateAssign {
-		rhs, err := d.GetMatchingNodes(context, expressionNode.Rhs)
+		rhs, err := d.GetMatchingNodes(context.ReadOnlyClone(), expressionNode.Rhs)
 		if err != nil {
 			return Context{}, err
 		}
@@ -32,7 +32,7 @@ func assignTagOperator(d *dataTreeNavigator, context Context, expressionNode *Ex
 		candidate := el.Value.(*CandidateNode)
 		log.Debugf("Setting tag of : %v", candidate.GetKey())
 		if expressionNode.Operation.UpdateAssign {
-			rhs, err := d.GetMatchingNodes(context.SingleChildContext(candidate), expressionNode.Rhs)
+			rhs, err := d.GetMatchingNodes(context.SingleReadonlyChildContext(candidate), expressionNode.Rhs)
 			if err != nil {
 				return Context{}, err
 			}
diff --git a/pkg/yqlib/operator_union_test.go b/pkg/yqlib/operator_union_test.go
index 4171929..417e86b 100644
--- a/pkg/yqlib/operator_union_test.go
+++ b/pkg/yqlib/operator_union_test.go
@@ -5,6 +5,20 @@ import (
 )
 
 var unionOperatorScenarios = []expressionScenario{
+	// {
+	// 	skipDoc:    true,
+	// 	document:   "{}",
+	// 	expression: `(.a, .b.c) as $x`,
+	// 	expected: []string{
+	// 		"D0, P[], (doc)::{}\n",
+	// 	},
+	// },
+	// {
+	// 	skipDoc:    true,
+	// 	document:   "{}",
+	// 	expression: `(.a, .b.c)`,
+	// 	expected:   []string{},
+	// },
 	{
 		description: "Combine scalars",
 		expression:  `1, true, "cat"`,
diff --git a/pkg/yqlib/operator_variables.go b/pkg/yqlib/operator_variables.go
index 9c498cb..5208132 100644
--- a/pkg/yqlib/operator_variables.go
+++ b/pkg/yqlib/operator_variables.go
@@ -16,7 +16,7 @@ func getVariableOperator(d *dataTreeNavigator, context Context, expressionNode *
 }
 
 func assignVariableOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
-	lhs, err := d.GetMatchingNodes(context, expressionNode.Lhs)
+	lhs, err := d.GetMatchingNodes(context.ReadOnlyClone(), expressionNode.Lhs)
 	if err != nil {
 		return Context{}, nil
 	}
diff --git a/pkg/yqlib/operator_variables_test.go b/pkg/yqlib/operator_variables_test.go
index b0fe20a..68ccac1 100644
--- a/pkg/yqlib/operator_variables_test.go
+++ b/pkg/yqlib/operator_variables_test.go
@@ -5,6 +5,14 @@ import (
 )
 
 var variableOperatorScenarios = []expressionScenario{
+	{
+		skipDoc:    true,
+		document:   `{}`,
+		expression: `.a.b as $foo`,
+		expected: []string{
+			"D0, P[], (doc)::{}\n",
+		},
+	},
 	{
 		description: "Single value variable",
 		document:    `a: cat`,