--- a/src/firewall/config/__init__.py.in
+++ b/src/firewall/config/__init__.py.in
@@ -80,7 +80,8 @@
     FIREWALLD_POLICIES = path + "/policies"
 
 
-set_default_config_paths("/usr/lib/firewalld")
+import os
+set_default_config_paths(os.environ.get("NIX_FIREWALLD_CONFIG_PATH", "/usr/lib/firewalld"))
 
 FIREWALLD_LOGFILE = "/var/log/firewalld"