diff --git a/etc/default.nix b/etc/default.nix
index 450d96efc49..1e7f3dc7dd9 100644
--- a/etc/default.nix
+++ b/etc/default.nix
@@ -45,7 +45,10 @@ import ../helpers/make-etc.nix {
     }
 
     { # Hostname-to-IP mappings.
-      source = ./hosts;
+      source = pkgs.substituteAll{
+	src = ./hosts;
+	extraHosts = config.get ["networking" "extraHosts"];
+	};
       target = "hosts";
     }
 
diff --git a/etc/hosts b/etc/hosts
index 75721cd5afd..2774e092d85 100644
--- a/etc/hosts
+++ b/etc/hosts
@@ -1 +1,2 @@
 127.0.0.1 localhost
+@extraHosts@
diff --git a/system/options.nix b/system/options.nix
index 182653a1e6c..4e28b48d413 100644
--- a/system/options.nix
+++ b/system/options.nix
@@ -235,6 +235,12 @@
     description = "The name of the machine.";
   }
 
+  {
+	name = ["networking" "extraHosts"];
+	default = "";
+	example = "192.168.0.1 lanlocalhost";
+	description = "Pasted verbatim into /etc/hosts.";
+  }
 
   {
     name = ["networking" "useDHCP"];