diff --git a/lib/latch/error/store.ex b/lib/latch/error/store.ex
index 919e0db..6805296 100644
--- a/lib/latch/error/store.ex
+++ b/lib/latch/error/store.ex
@@ -14,6 +14,8 @@ defmodule Latch.Error.Store do
     * `:delete_expired_requests`
   """
 
+  alias Latch.Store, as: StoreBehavior
+
   defexception [:action, :did, :reason]
 
   @type action ::
@@ -25,7 +27,11 @@ defmodule Latch.Error.Store do
           | :put_request
           | :delete_expired_requests
 
-  @type t :: %__MODULE__{action: action(), did: String.t() | nil, reason: term() | nil}
+  @type t :: %__MODULE__{
+          action: action(),
+          did: String.t() | nil,
+          reason: StoreBehavior.reason()
+        }
 
   @impl Exception
   def message(%__MODULE__{action: action, did: did, reason: reason}) do
diff --git a/lib/latch/store.ex b/lib/latch/store.ex
index 3ff3503..f6b2869 100644
--- a/lib/latch/store.ex
+++ b/lib/latch/store.ex
@@ -16,8 +16,9 @@ defmodule Latch.Store do
 
   @type state :: binary()
   @type did :: binary()
-  # TODO fix the term here, it should be specific atoms not "something"
-  @type store_error :: {:error, :not_found} | {:error, term()}
+
+  @type reason :: :not_found | :backend_error
+  @type store_error :: {:error, reason()}
 
   @doc """
   Store an inflight request under `state` for at least `ttl_seconds`.