diff --git a/lib/splode/error.ex b/lib/splode/error.ex
index 2160496..4c8567c 100644
--- a/lib/splode/error.ex
+++ b/lib/splode/error.ex
@@ -123,7 +123,7 @@ defmodule Splode.Error do
 
           Enum.reduce(List.wrap(vars), string, fn {key, value}, acc ->
             if String.contains?(acc, "%{#{key}}") do
-              String.replace(acc, "%{#{key}}", to_string(value))
+              String.replace(acc, "%{#{key}}", inspect(value))
             else
               acc
             end
diff --git a/test/splode/error_test.exs b/test/splode/error_test.exs
new file mode 100644
index 0000000..26965f7
--- /dev/null
+++ b/test/splode/error_test.exs
@@ -0,0 +1,12 @@
+defmodule Splode.ErrorTest do
+  use ExUnit.Case
+
+  defmodule InvalidAttribute do
+    use Splode.Error, fields: [:message], class: :invalid
+  end
+
+  test "message" do
+    invalid = %InvalidAttribute{message: "must be in %{list}", vars: [list: [:foo, :bar]]}
+    assert "must be in [:foo, :bar]" == invalid |> Exception.message()
+  end
+end