diff --git a/lib/peri.ex b/lib/peri.ex
index 9e3ed07..37730b8 100644
--- a/lib/peri.ex
+++ b/lib/peri.ex
@@ -300,7 +300,7 @@ defmodule Peri do
   end
 
   defp enumerable_has_key?(data, key) when is_map(data) do
-    Map.has_key?(data, key) or Map.has_key?(data, Atom.to_string(key))
+    Map.has_key?(data, key) or Map.has_key?(data, (is_binary(key) && key) || Atom.to_string(key))
   end
 
   defp enumerable_has_key?(data, key) when is_list(data) do
@@ -334,7 +334,7 @@ defmodule Peri do
 
   defp get_enumerable_value(enum, key) do
     case Access.get(enum, key) do
-      nil when is_map(enum) -> Map.get(enum, Atom.to_string(key))
+      nil when is_map(enum) -> Map.get(enum, (is_binary(key) && key) || Atom.to_string(key))
       val -> val
     end
   end
diff --git a/mix.exs b/mix.exs
index 7a299e7..a7cc49d 100644
--- a/mix.exs
+++ b/mix.exs
@@ -1,7 +1,7 @@
 defmodule Peri.MixProject do
   use Mix.Project
 
-  @version "0.2.6"
+  @version "0.2.7"
   @source_url "https://github.com/zoedsoupe/peri"
 
   def project do
diff --git a/test/peri_test.exs b/test/peri_test.exs
index 4a22949..086433c 100644
--- a/test/peri_test.exs
+++ b/test/peri_test.exs
@@ -9,6 +9,12 @@ defmodule PeriTest do
     email: {:required, :string}
   })
 
+  defschema(:simple_mixed_keys, %{
+    "email" => {:required, :string},
+    name: :string,
+    age: :integer
+  })
+
   defschema(:nested, %{
     user: %{
       name: :string,
@@ -68,6 +74,13 @@ defmodule PeriTest do
              } =
                simple(data)
     end
+
+    test "does not raise on simple schema with string keys" do
+      data = %{name: "John", age: 30}
+
+      assert {:error, [%Peri.Error{path: ["email"], message: "is required"}]} =
+               simple_mixed_keys(data)
+    end
   end
 
   describe "nested schema validation" do