diff --git a/tools/testing/selftests/net/forwarding/lib.sh b/tools/testing/selftests/net/forwarding/lib.sh
index eabbdf00d8ca..9086d2015296 100644
--- a/tools/testing/selftests/net/forwarding/lib.sh
+++ b/tools/testing/selftests/net/forwarding/lib.sh
@@ -1134,12 +1134,19 @@ bridge_ageing_time_get()
 }
 
 declare -A SYSCTL_ORIG
+sysctl_save()
+{
+	local key=$1; shift
+
+	SYSCTL_ORIG[$key]=$(sysctl -n $key)
+}
+
 sysctl_set()
 {
 	local key=$1; shift
 	local value=$1; shift
 
-	SYSCTL_ORIG[$key]=$(sysctl -n $key)
+	sysctl_save "$key"
 	sysctl -qw $key="$value"
 }