diff --git a/lib/req/test.ex b/lib/req/test.ex
index db79af71..8d5ffe78 100644
--- a/lib/req/test.ex
+++ b/lib/req/test.ex
@@ -218,6 +218,26 @@ defmodule Req.Test do
 
   @doc false
   def call(conn, stub_name) do
-    stub(stub_name).(conn)
+    case stub(stub_name) do
+      fun when is_function(fun) ->
+        fun.(conn)
+
+      module when is_atom(module) ->
+        module.call(conn, module.init([]))
+
+      {module, options} when is_atom(module) ->
+        module.call(conn, module.init(options))
+
+      other ->
+        raise """
+        expected stub to be one of:
+
+          * 0-arity function
+          * module
+          * {module, options}
+
+        got: #{inspect(other)}\
+        """
+    end
   end
 end
diff --git a/test/req/test_test.exs b/test/req/test_test.exs
index 98ecb6d0..ddf9a14f 100644
--- a/test/req/test_test.exs
+++ b/test/req/test_test.exs
@@ -22,12 +22,25 @@ defmodule Req.TestTest do
     assert Req.Test.stub(:foo) == 2
   end
 
-  test "plug" do
-    Req.Test.stub(:foo, fn conn ->
-      Plug.Conn.send_resp(conn, 200, "hi")
-    end)
+  describe "plug" do
+    test "function" do
+      Req.Test.stub(:foo, fn conn ->
+        Plug.Conn.send_resp(conn, 200, "hi")
+      end)
+
+      assert Req.get!(plug: {Req.Test, :foo}).body == "hi"
+    end
 
-    assert Req.get!(plug: {Req.Test, :foo}).body == "hi"
+    test "module" do
+      defmodule Foo do
+        def init(options), do: options
+        def call(conn, []), do: Plug.Conn.send_resp(conn, 200, "hi")
+      end
+
+      Req.Test.stub(:foo, Foo)
+
+      assert Req.get!(plug: {Req.Test, :foo}).body == "hi"
+    end
   end
 
   describe "allow/3" do