diff --git a/lib/numerus/formatter.ex b/lib/numerus/formatter.ex
index 0a50603..9742cc6 100644
--- a/lib/numerus/formatter.ex
+++ b/lib/numerus/formatter.ex
@@ -48,27 +48,60 @@ defmodule Numerus.Formatter do
 
   iex> Numerus.Formatter.normalize("12065551212")
   "+12065551212"
+
+  iex> Numerus.Formatter.normalize("98655") # shortcode
+  "98655"
+
+  iex> Numerus.Formatter.normalize("+12065551212", :one_npan)
+  "12065551212"
   ```
+
+  iex> Numerus.Formatter.normalize("98655", :e164)
+  {:error, :invalid_format}
   """
   @spec normalize(did :: bitstring, format :: atom() | nil) :: bitstring() | {:error, :invalid_format}
-  def normalize(did, format) do
+  def normalize(did, format) when is_bitstring(did) and is_atom(format) do
     case format do
       :e164       -> to_e164(did)
       :npan       -> to_npan(did)
       :one_npan   -> to_1npan(did)
       :us_intl    -> to_usintl(did)
-      :shortcode  -> did
+      :shortcode  ->
+        # we need to verify that the supplied number is a shortcode. If so,
+        # return the did, if not, then return an error as this conversion is
+        # not possible.
+        case Classifier.classify(did) do
+          {:ok, %{"region" => _, "format" => format}} ->
+            case format do
+              :shortcode  -> did
+              _           -> {:error, :invalid_format}
+            end
+        end
+      _           -> {:error, :invalid_format}
       _           -> {:error, :invalid_format}
     end
   end
 
-  def normalize(did), do: normalize(did, @normal_format)
+  def normalize(_,_), do: {:error, :invalid_format}
+
+  def normalize(did) when is_bitstring(did) do
+    case Classifier.classify(did) do
+      {:ok, %{"region" => _, "format" => format}} ->
+        if format == :shortcode do
+          did
+        else
+          normalize(did, @normal_format)
+        end
+      _ -> {:error, :invalid_format}
+    end
+  end
+  def normalize(_), do: {:error, :invalid_format}
 
   @doc """
   Pretty format a telephone number. For NADP numbers. Other numbers will
   be returned with the country code separated from the main number.
   """
-  @spec format(did :: bitstring()) :: bitstring() | :error
+  @spec format(did :: bitstring()) :: bitstring() | {:error, :invalid_format}
   def format(did) when is_bitstring(did) do
     case Classifier.classify(did) do
       {:ok, %{"region" => region, "format" => _}} ->
@@ -90,14 +123,14 @@ defmodule Numerus.Formatter do
       _ -> did
     end
   end
-  def format(_), do: :error
+  def format(_), do: {:error, :invalid_format}
 
   # -- convert functions -- #
 
   @doc """
   Convert the supplied did to E.164
   """
-  @spec to_e164(did :: bitstring()) :: bitstring() | :error
+  @spec to_e164(did :: bitstring()) :: bitstring() | {:error, :invalid_format}
   def to_e164(did) when is_bitstring(did) do
     case Classifier.classify(did) do
       {:ok, %{"region" => _, "format" => format}} ->
@@ -106,7 +139,7 @@ defmodule Numerus.Formatter do
           :one_npan   -> "+#{did}"
           :npan       -> "+1#{did}"
           :us_intl    -> String.replace(did, ~r/^011/, "+")
-          _           -> :error
+          _           -> {:error, :invalid_format}
         end
       _ ->
         # we do not convert other formats, so just return an error.
@@ -119,7 +152,7 @@ defmodule Numerus.Formatter do
   @doc """
   Convert the supplied did to npan
   """
-  @spec to_npan(did :: bitstring()) :: bitstring() | :error
+  @spec to_npan(did :: bitstring()) :: bitstring() | {:error, :invalid_format}
   def to_npan(did) when is_bitstring(did) do
     case Classifier.classify(did) do
       {:ok, %{"region" => region, "format" => format}} ->
@@ -133,19 +166,22 @@ defmodule Numerus.Formatter do
               :e164     -> String.replace(did, ~r/\+1/, "")
               :one_npan -> String.replace(did, ~r/^1/,  "")
               :npan     -> did
+              _         -> {:error, :invalid_format}
             end
+
+          _ -> {:error, :invalid_format}
         end
       _ ->
         # we do not convert other regions. just return an error.
         :error
     end
   end
-  def to_npan(_), do: :error
+  def to_npan(_), do: {:error, :invalid_format}
 
   @doc """
   Convert the supplied did to 1npan
   """
-  @spec to_1npan(did :: bitstring()) :: bitstring() | :error
+  @spec to_1npan(did :: bitstring()) :: bitstring() | {:error, :invalid_format}
   def to_1npan(did) when is_bitstring(did) do
     case Classifier.classify(did) do
       {:ok, %{"region" => region, "format" => format}} ->
@@ -159,14 +195,17 @@ defmodule Numerus.Formatter do
               :e164     -> String.replace(did, ~r/\+/, "")
               :one_npan -> did
               :npan     -> "1#{did}"
+              _         -> {:error, :invalid_format}
             end
+
+          _ -> {:error, :invalid_format}
         end
       _ ->
         # we do not convert other regions. just return an error.
         :error
     end
   end
-  def to_1npan(_), do: :error
+  def to_1npan(_), do: {:error, :invalid_format}
 
   @doc """
   Convert the supplied did to us intl format.
@@ -181,11 +220,13 @@ defmodule Numerus.Formatter do
             case format do
               :us_intl  -> did
               :e164     -> String.replace(did, ~r/\+/, "011")
+              _         -> {:error, :invalid_format}
             end
+          _ -> {:error, :invalid_format}
         end
     end
   end
-  def to_usintl(_), do: :error
+  def to_usintl(_), do: {:error, :invalid_format}
 
   # -- format  functions -- #
 end
diff --git a/mix.exs b/mix.exs
index c1b1081..7f5c416 100644
--- a/mix.exs
+++ b/mix.exs
@@ -26,7 +26,7 @@ defmodule Numerus.MixProject do
   def project do
     [
       app: :numerus,
-      version: "0.1.3",
+      version: "0.1.4",
       elixir: "~> 1.14",
       start_permanent: Mix.env() == :prod,
       deps: deps(),