diff --git a/lib/ex_parameterized/params.ex b/lib/ex_parameterized/params.ex
index e7f419c..f0dfbbc 100644
--- a/lib/ex_parameterized/params.ex
+++ b/lib/ex_parameterized/params.ex
@@ -51,7 +51,10 @@ defmodule ExUnit.Parameterized.Params do
     end
   end
 
-  defp param_with_index(list) do
+  defp param_with_index(list) when is_list(list) do
     Enum.zip(list, 0..Enum.count(list))
   end
+  defp param_with_index(list) do
+    raise(ArgumentError, message: "Unsupported format")
+  end
 end
diff --git a/lib/ex_parameterized/params_callback.ex b/lib/ex_parameterized/params_callback.ex
index 22503c4..36bbfa1 100644
--- a/lib/ex_parameterized/params_callback.ex
+++ b/lib/ex_parameterized/params_callback.ex
@@ -54,7 +54,10 @@ defmodule ExUnit.Parameterized.ParamsCallback do
     end
   end
 
-  defp param_with_index(list) do
+  defp param_with_index(list) when is_list(list) do
     Enum.zip(list, 0..Enum.count(list))
   end
+  defp param_with_index(list) do
+    raise(ArgumentError, message: "Unsupported format")
+  end
 end
diff --git a/test/ex_parameterized_callback_test.exs b/test/ex_parameterized_callback_test.exs
index 786e86f..6644a99 100644
--- a/test/ex_parameterized_callback_test.exs
+++ b/test/ex_parameterized_callback_test.exs
@@ -119,4 +119,13 @@ defmodule ExParameterizedParamsCallbackTest do
       "description for param2": {"hello", context[:hello], "hello and world"}
     ]
   end
+
+  test_with_params "with function", fn p ->
+    p
+  end do
+    make = fn a -> a + 1 end
+    [
+      {make.(1)}
+    ]
+  end
 end
diff --git a/test/ex_parameterized_test.exs b/test/ex_parameterized_test.exs
index 9699fcd..9d1c258 100644
--- a/test/ex_parameterized_test.exs
+++ b/test/ex_parameterized_test.exs
@@ -153,4 +153,13 @@ defmodule ExParameterizedTest do
   end do
     Enum.map([{["a", "b"]}], fn x -> x end)
   end
+
+  test_with_params "with function", fn p ->
+      p
+  end do
+    make = fn a -> a + 1 end
+    [
+      {make.(1)}
+    ]
+  end
 end