diff --git a/filter_linux.go b/filter_linux.go
index a0e000c..dc0f90a 100644
--- a/filter_linux.go
+++ b/filter_linux.go
@@ -141,19 +141,19 @@ func (h *Handle) FilterAdd(filter Filter) error {
 		}
 
 		if native != networkOrder {
-			// Copy Tcu32Sel.
-			cSel := sel
+			// Copy TcU32Sel.
+			cSel := *sel
 			keys := make([]nl.TcU32Key, cap(sel.Keys))
 			copy(keys, sel.Keys)
 			cSel.Keys = keys
-			sel = cSel
+			sel = &cSel
 
 			// Handle the endianness of attributes
 			sel.Offmask = native.Uint16(htons(sel.Offmask))
 			sel.Hmask = native.Uint32(htonl(sel.Hmask))
-			for _, key := range sel.Keys {
-				key.Mask = native.Uint32(htonl(key.Mask))
-				key.Val = native.Uint32(htonl(key.Val))
+			for i, key := range sel.Keys {
+				sel.Keys[i].Mask = native.Uint32(htonl(key.Mask))
+				sel.Keys[i].Val = native.Uint32(htonl(key.Val))
 			}
 		}
 		sel.Nkeys = uint8(len(sel.Keys))
@@ -453,9 +453,9 @@ func parseU32Data(filter Filter, data []syscall.NetlinkRouteAttr) (bool, error)
 				// Handle the endianness of attributes
 				u32.Sel.Offmask = native.Uint16(htons(sel.Offmask))
 				u32.Sel.Hmask = native.Uint32(htonl(sel.Hmask))
-				for _, key := range u32.Sel.Keys {
-					key.Mask = native.Uint32(htonl(key.Mask))
-					key.Val = native.Uint32(htonl(key.Val))
+				for i, key := range u32.Sel.Keys {
+					u32.Sel.Keys[i].Mask = native.Uint32(htonl(key.Mask))
+					u32.Sel.Keys[i].Val = native.Uint32(htonl(key.Val))
 				}
 			}
 		case nl.TCA_U32_ACT:
diff --git a/filter_test.go b/filter_test.go
index 64ab757..3f4be0d 100644
--- a/filter_test.go
+++ b/filter_test.go
@@ -3,6 +3,7 @@
 package netlink
 
 import (
+	"reflect"
 	"syscall"
 	"testing"
 )
@@ -193,9 +194,16 @@ func TestAdvancedFilterAddDel(t *testing.T) {
 		ClassId: classId,
 		Actions: []Action{},
 	}
+	// Copy filter.
+	cFilter := *filter
 	if err := FilterAdd(filter); err != nil {
 		t.Fatal(err)
 	}
+	// Check if the filter is identical before and after FilterAdd.
+	if !reflect.DeepEqual(cFilter, *filter) {
+		t.Fatal("U32 %v and %v are not equal", cFilter, *filter)
+	}
+
 	filters, err := FilterList(link, qdiscHandle)
 	if err != nil {
 		t.Fatal(err)