diff --git a/pkg/pipeline/transform/transform_filter.go b/pkg/pipeline/transform/transform_filter.go
index 3cae2a7f1..bd2783177 100644
--- a/pkg/pipeline/transform/transform_filter.go
+++ b/pkg/pipeline/transform/transform_filter.go
@@ -32,6 +32,7 @@ func (f *Filter) Transform(input []config.GenericMap) []config.GenericMap {
 	log.Debugf("f = %v", f)
 	output := make([]config.GenericMap, 0)
 	for _, entry := range input {
+		// copy input entry before transform to avoid alteration on parallel stages
 		outputEntry := entry.Copy()
 		addToOutput := true
 		for _, rule := range f.Rules {
diff --git a/pkg/pipeline/transform/transform_network.go b/pkg/pipeline/transform/transform_network.go
index 2bb45723f..68bcac3d7 100644
--- a/pkg/pipeline/transform/transform_network.go
+++ b/pkg/pipeline/transform/transform_network.go
@@ -49,6 +49,7 @@ func (n *Network) Transform(input []config.GenericMap) []config.GenericMap {
 }
 
 func (n *Network) TransformEntry(inputEntry config.GenericMap) config.GenericMap {
+	// copy input entry before transform to avoid alteration on parallel stages
 	outputEntry := inputEntry.Copy()
 
 	for _, rule := range n.Rules {