diff --git a/checkmate.nix b/checkmate.nix
index a0bff8d..f22d5d9 100644
--- a/checkmate.nix
+++ b/checkmate.nix
@@ -203,6 +203,23 @@ in
           expected = [ ./tree/modules/hello-world/mod.nix ];
         };
 
+        import-tree."test passes non-paths without string conversion" = {
+          expr =
+            let
+              mod = it [
+                {
+                  options.hello = lib.mkOption {
+                    default = "world";
+                    type = lib.types.str;
+                  };
+                }
+              ];
+              res = lib.modules.evalModules { modules = [ mod ]; };
+            in
+            res.config.hello;
+          expected = "world";
+        };
+
         import-tree."test can take other import-trees as if they were paths" = {
           expr = (lit.filter (lib.hasInfix "mod")).leafs [
             (it.addPath ./tree/modules/hello-option)
diff --git a/default.nix b/default.nix
index 9ee0c97..b8ae573 100644
--- a/default.nix
+++ b/default.nix
@@ -35,11 +35,13 @@ let
               treeFiles x
             else if hasOutPath x then
               listFilesRecursive x.outPath
-            else if lib.pathIsDirectory x then
+            else if isDirectory x then
               lib.filesystem.listFilesRecursive x
             else
               [ x ];
           treeFiles = t: (t.withLib lib).leafs.result;
+          pathFilter = compose (and filterf initialFilter) toString;
+          filter = x: if isPathLike x then pathFilter x else filterf x;
         in
         lib.pipe
           [ paths root ]
@@ -47,7 +49,7 @@ let
             (lib.lists.flatten)
             (map listFilesRecursive)
             (lib.lists.flatten)
-            (builtins.filter (compose (and filterf initialFilter) toString))
+            (builtins.filter filter)
             (map mapf)
           ];
 
@@ -71,6 +73,10 @@ let
     attrs: k: f:
     attrs // { ${k} = f attrs.${k}; };
 
+  isDirectory = and (x: builtins.readFileType x == "directory") isPathLike;
+
+  isPathLike = x: builtins.isPath x || builtins.isString x || hasOutPath x;
+
   hasOutPath = and (x: x ? outPath) builtins.isAttrs;
 
   isImportTree = and (x: x ? __config.__functor) builtins.isAttrs;