diff --git a/nixos/modules/services/networking/firewall.nix b/nixos/modules/services/networking/firewall.nix
index 15aaf7410674..b0045ff795e3 100644
--- a/nixos/modules/services/networking/firewall.nix
+++ b/nixos/modules/services/networking/firewall.nix
@@ -546,7 +546,7 @@ in
       options nf_conntrack nf_conntrack_helper=1
     '';
 
-    assertions = [ { assertion = (cfg.checkReversePath != false) || kernelHasRPFilter;
+    assertions = [ { assertion = cfg.checkReversePath -> kernelHasRPFilter;
                      message = "This kernel does not support rpfilter"; }
                  ];