diff --git a/imageroot/actions/create-module/40strict_interface_validation b/imageroot/actions/create-module/40strict_interface_validation
new file mode 100755
index 0000000..cef5bb1
--- /dev/null
+++ b/imageroot/actions/create-module/40strict_interface_validation
@@ -0,0 +1,10 @@
+#!/usr/bin/env python3
+
+#
+# Copyright (C) 2024 Nethesis S.r.l.
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+
+import agent
+
+agent.set_env("DNSMASQ_STRICT_INTERFACE_VALIDATION", 1)
diff --git a/imageroot/pypkg/network.py b/imageroot/pypkg/network.py
index 230d484..f1ab585 100644
--- a/imageroot/pypkg/network.py
+++ b/imageroot/pypkg/network.py
@@ -72,7 +72,7 @@ def list_interfaces():
     """
     subprocess_result = subprocess.run(["ip", "-4", "-j", "addr"], check=True, capture_output=True)
     interfaces = [__format_interface(interface) for interface in json.loads(subprocess_result.stdout) if __filter_interface(interface)]
-    if os.environ.get('DNSMASQ_RELAXED_INTERFACE_VALIDATION', "0") == "0":
+    if os.environ.get('DNSMASQ_STRICT_INTERFACE_VALIDATION', "0") == "1":
         interfaces = [interface for interface in interfaces if interface['addresses'][0]['network'].is_private]
     return interfaces