diff --git a/flake.nix b/flake.nix
index 43c5853..16d0295 100644
--- a/flake.nix
+++ b/flake.nix
@@ -43,9 +43,11 @@
             bool
             nullOr
             lines
+            str
             path
             int
             attrsOf
+            either
             ;
           fileType = submodule (
             { options, ... }:
@@ -63,7 +65,7 @@
                 };
 
                 source = mkOption {
-                  type = nullOr path;
+                  type = nullOr (either path str);
                   default = null;
                   description = "Path of the source file or directory";
                 };