diff --git a/README.md b/README.md
index ac728e5..249afaa 100644
--- a/README.md
+++ b/README.md
@@ -63,6 +63,8 @@ The second argument to `with-inputs` is an attribute set that
 can be used to drive input resolution, for example to use local
 checkout or to specify flake-like follows.
 
+See [tests.nix](./tests.nix) for usage examples.
+
 ```nix
 {
     # Local checkout — loaded as a flake if a flake.nix is present
@@ -92,6 +94,9 @@ checkout or to specify flake-like follows.
         inputs.nixpkgs.follows = "nixpkgs";
         inputs.utils.follows   = "flake-utils";
     };
+
+    # Takes the original sources.otherFlake and avoids flake call
+    otherFlake = source: source // { flake = false; };
 }
 ```
 
diff --git a/default.nix b/default.nix
index e627819..120036a 100644
--- a/default.nix
+++ b/default.nix
@@ -21,14 +21,18 @@ let
 
   isFollows = v: builtins.isAttrs v && v ? follows;
 
+  specKeys = [
+    "follows"
+    "inputs"
+  ];
+
   # A spec is an attrset whose only keys are "follows" and/or "inputs",
   # where every inputs.* value is itself a follows spec.
   # Anything with outPath, lib, packages, … is a direct value, not a spec.
   isSpec =
     v:
     builtins.isAttrs v
-    && (v ? follows || v ? inputs)
-    && builtins.all (k: k == "follows" || k == "inputs") (builtins.attrNames v)
+    && builtins.all (x: builtins.elem x specKeys) (builtins.attrNames v)
     && (!(v ? inputs) || builtins.all (k: isFollows v.inputs.${k}) (builtins.attrNames v.inputs));
 
   # Returns the resolved input, or null if any segment in the path is missing.
@@ -58,7 +62,9 @@ let
   # Values with outPath but no _type go through mkInput so their flake.nix is loaded.
   resolveInput =
     name: v:
-    if isFollows v then
+    if builtins.isFunction v then
+      resolveInput name (v sources.${name})
+    else if isFollows v then
       if v.follows == "" then { } else walkPath v.follows
     else if isSpec v then
       resolvedSources.${name} or { }
@@ -90,12 +96,14 @@ let
   mkInput =
     name: sourceInfo:
     let
+      isFlake = sourceInfo.flake or true;
       flakePath = sourceInfo.outPath + "/flake.nix";
+      flakeExists = sourceInfo ? outPath && builtins.pathExists flakePath;
     in
-    if sourceInfo ? outPath && builtins.pathExists flakePath then
+    if isFlake && flakeExists then
       mkFlakeInput name sourceInfo (import flakePath)
     else
-      sourceInfo;
+      sourceInfo // { inherit sourceInfo; };
 
   mkFlakeInput =
     name: sourceInfo: flake:
diff --git a/tests.nix b/tests.nix
index ccecc8a..1b87ab7 100644
--- a/tests.nix
+++ b/tests.nix
@@ -362,4 +362,30 @@ in
     expected = npins.nixpkgs.outPath;
   };
 
+  "test non flakes are not evaluated" = {
+    expr =
+      (with-inputs
+        {
+          yesFlake.outPath = ./fixtures/fake-flake;
+          nonFlake.outPath = ./fixtures/fake-flake;
+        }
+        {
+          nonFlake = source: source // { flake = false; };
+        }
+        (inputs: {
+          result.yes.hasOutputs = inputs.yesFlake ? outputs;
+          result.non.hasOutputs = inputs.nonFlake ? outputs;
+
+          result.non.sourceInfo = inputs.nonFlake.sourceInfo;
+        })
+      ).result;
+    expected = {
+      yes.hasOutputs = true;
+      non.hasOutputs = false;
+
+      non.sourceInfo.flake = false;
+      non.sourceInfo.outPath = ./fixtures/fake-flake;
+    };
+  };
+
 }