diff --git a/lib/cassette/client/generate_st.ex b/lib/cassette/client/generate_st.ex
index cadf947..4bcfa9c 100644
--- a/lib/cassette/client/generate_st.ex
+++ b/lib/cassette/client/generate_st.ex
@@ -7,6 +7,8 @@ defmodule Cassette.Client.GenerateSt do
 
   alias Cassette.Config
   alias Cassette.Client
+  alias HTTPoison.Error
+  alias HTTPoison.Response
 
   @type response ::
           {:error, :bad_tgt}
@@ -26,15 +28,18 @@ defmodule Cassette.Client.GenerateSt do
     headers = []
 
     case post(url, params, headers, options) do
-      {:ok, %HTTPoison.Response{status_code: 404}} ->
+      {:ok, %Response{status_code: 404}} ->
         {:error, :bad_tgt}
 
-      {:ok, %HTTPoison.Response{status_code: 200, body: body}} ->
+      {:ok, %Response{status_code: 200, body: body}} ->
         {:ok, body}
 
-      {:ok, %HTTPoison.Response{status_code: status_code, body: body}} ->
+      {:ok, %Response{status_code: status_code, body: body}} ->
         {:fail, status_code, body}
 
+      {:error, %Error{reason: reason}} ->
+        {:fail, reason}
+
       _ ->
         {:fail, :unknown}
     end
diff --git a/lib/cassette/client/generate_tgt.ex b/lib/cassette/client/generate_tgt.ex
index a26d1cb..ab55953 100644
--- a/lib/cassette/client/generate_tgt.ex
+++ b/lib/cassette/client/generate_tgt.ex
@@ -7,13 +7,13 @@ defmodule Cassette.Client.GenerateTgt do
 
   alias Cassette.Config
   alias Cassette.Client
+  alias HTTPoison.Error
   alias HTTPoison.Response
 
   @type response ::
           {:error, :bad_credentials}
           | {:ok, String.t()}
-          | {:fail, pos_integer()}
-          | {:fail, :unknown}
+          | {:fail, term()}
 
   @spec process_headers([{String.t(), String.t()}]) :: %{String.t() => String.t()}
   defp process_headers(headers) do
@@ -42,6 +42,9 @@ defmodule Cassette.Client.GenerateTgt do
       {:ok, %Response{status_code: status_code}} ->
         {:fail, status_code}
 
+      {:error, %Error{reason: reason}} when is_atom(reason) ->
+        {:fail, reason}
+
       _ ->
         {:fail, :unknown}
     end
diff --git a/lib/cassette/client/validate_ticket.ex b/lib/cassette/client/validate_ticket.ex
index bdd01e3..ab23e43 100644
--- a/lib/cassette/client/validate_ticket.ex
+++ b/lib/cassette/client/validate_ticket.ex
@@ -7,9 +7,10 @@ defmodule Cassette.Client.ValidateTicket do
 
   alias Cassette.Config
   alias Cassette.Client
+  alias HTTPoison.Error
   alias HTTPoison.Response
 
-  @type response :: {:ok, String.t()} | {:fail, :unknown}
+  @type response :: {:ok, String.t()} | {:fail, term()}
 
   @doc """
   Do request to cas service to validate a service ticket
@@ -22,6 +23,7 @@ defmodule Cassette.Client.ValidateTicket do
 
     case get(url, headers, options) do
       {:ok, %Response{status_code: 200, body: body}} -> {:ok, body}
+      {:error, %Error{reason: reason}} when is_atom(reason) -> {:fail, reason}
       _ -> {:fail, :unknown}
     end
   end
diff --git a/lib/cassette/server.ex b/lib/cassette/server.ex
index fa59491..7f0cbd6 100644
--- a/lib/cassette/server.ex
+++ b/lib/cassette/server.ex
@@ -62,7 +62,7 @@ defmodule Cassette.Server do
     GenServer.start_link(__MODULE__, {:ok, config})
   end
 
-  version(">= 1.5.0") do
+  version ">= 1.5.0" do
     def child_spec([name, config = %Config{}]) do
       defaults = %{id: name, start: {__MODULE__, :start_link, [name, config]}}
       Supervisor.child_spec(defaults, [])
@@ -178,6 +178,9 @@ defmodule Cassette.Server do
       {:fail, :unknown} ->
         {:reply, {:error, "Failed for unknown reason"}, state}
 
+      {:fail, reason} when is_atom(reason) ->
+        {:reply, {:error, "Failed because #{reason}"}, state}
+
       {:fail, status_code} ->
         {:reply, {:error, "Failed with status #{status_code}"}, state}
     end
@@ -236,6 +239,9 @@ defmodule Cassette.Server do
 
       {:fail, :unknown} ->
         {:error, "Failed for unknown reason"}
+
+      {:fail, reason} ->
+        {:error, "Failed because #{reason}"}
     end
   end
 
diff --git a/test/cassette/client/generate_st_test.exs b/test/cassette/client/generate_st_test.exs
index 241cca9..78fb82d 100644
--- a/test/cassette/client/generate_st_test.exs
+++ b/test/cassette/client/generate_st_test.exs
@@ -27,10 +27,10 @@ defmodule Cassette.Client.GenerateStTest do
     assert {:fail, 418, "I. am. a. freaking. teapot."} = Cassette.Client.GenerateSt.perform(config, tgt, service)
   end
 
-  test "perform returns {:fail, :unknown} then http fails", %{bypass: bypass, config: config, tgt: tgt, service: service} do
+  test "perform returns {:fail, reason} then http fails with an atom", %{bypass: bypass, config: config, tgt: tgt, service: service} do
     Bypass.down(bypass)
 
-    assert {:fail, :unknown} = Cassette.Client.GenerateSt.perform(config, tgt, service)
+    assert {:fail, :econnrefused} = Cassette.Client.GenerateSt.perform(config, tgt, service)
   end
 
   test "perform generates a ST", %{bypass: bypass, config: config, tgt: tgt, service: service} do
diff --git a/test/cassette/client/generate_tgt_test.exs b/test/cassette/client/generate_tgt_test.exs
index d9ed9d5..ccb4c6e 100644
--- a/test/cassette/client/generate_tgt_test.exs
+++ b/test/cassette/client/generate_tgt_test.exs
@@ -17,6 +17,12 @@ defmodule Cassette.Client.GenerateTgtTest do
     assert {:error, :bad_credentials} = Cassette.Client.GenerateTgt.perform(config)
   end
 
+  test "perform returns {:fail, reason} for atom error reasons", %{bypass: bypass, config: config} do
+    Bypass.down(bypass)
+
+    assert {:fail, :econnrefused} = Cassette.Client.GenerateTgt.perform(config)
+  end
+
   test "perform returns {:fail, status_code} for other error statuses", %{bypass: bypass, config: config} do
     Bypass.expect bypass, fn conn ->
       conn |> Plug.Conn.resp(404, "not found")
diff --git a/test/cassette/client/validate_ticket_test.exs b/test/cassette/client/validate_ticket_test.exs
index 99dcbe1..f30d693 100644
--- a/test/cassette/client/validate_ticket_test.exs
+++ b/test/cassette/client/validate_ticket_test.exs
@@ -11,6 +11,12 @@ defmodule Cassette.Client.ValidateTicketTest do
     {:ok, bypass: bypass, config: config, ticket: ticket, service: service}
   end
 
+  test "perform returns {:fail, reason} for atom failure reasons", %{bypass: bypass, config: config, ticket: ticket, service: service} do
+    Bypass.down(bypass)
+
+    assert {:fail, :econnrefused} = Cassette.Client.ValidateTicket.perform(config, ticket, service)
+  end
+
   test "perform returns {:fail, :unknown} for not-200 response", %{bypass: bypass, config: config, ticket: ticket, service: service} do
     Bypass.expect bypass, fn conn ->
       conn |> Plug.Conn.resp(404, "not found")
@@ -19,12 +25,6 @@ defmodule Cassette.Client.ValidateTicketTest do
     assert {:fail, :unknown} = Cassette.Client.ValidateTicket.perform(config, ticket, service)
   end
 
-  test "perform returns {:fail, :unknown} then http fails", %{bypass: bypass, config: config, ticket: ticket, service: service} do
-    Bypass.down(bypass)
-
-    assert {:fail, :unknown} = Cassette.Client.ValidateTicket.perform(config, ticket, service)
-  end
-
   test "perform returns the validation body", %{bypass: bypass, config: config, ticket: ticket, service: service} do
     body = "<validation><result><xml /></result></validation>"
 
diff --git a/test/cassette/server_integration_test.exs b/test/cassette/server_integration_test.exs
index ea57fd2..9e4f487 100644
--- a/test/cassette/server_integration_test.exs
+++ b/test/cassette/server_integration_test.exs
@@ -19,7 +19,7 @@ defmodule Cassette.ServerIntegrationTest do
     assert {:ok, ^tgt} = Server.tgt(pid)
   end
 
-  test "fails with unknown reason when cas is down",
+  test "fails when cas is down",
     %{pid: pid, config: config} do
 
     {:ok, fake_cas_pid} = FakeCas.Server.start_link([])
@@ -28,7 +28,7 @@ defmodule Cassette.ServerIntegrationTest do
     :ok = Cassette.Server.reload(pid, config)
     FakeCas.Server.stop(fake_cas_pid)
 
-    assert {:error, "Failed for unknown reason"} = Server.tgt(pid)
+    assert {:error, "Failed because econnrefused"} = Server.tgt(pid)
   end
 
   test "fails with {:error, _} when username/password is invalid",