diff --git a/lib/money/ecto/money_ecto_composite_type.ex b/lib/money/ecto/money_ecto_composite_type.ex
index 60b73e7..4cd1c39 100644
--- a/lib/money/ecto/money_ecto_composite_type.ex
+++ b/lib/money/ecto/money_ecto_composite_type.ex
@@ -189,27 +189,11 @@ if Code.ensure_loaded?(Ecto.Type) do
     end
 
     def cast(%{"currency" => currency, "amount" => amount}, params)
-        when (is_binary(currency) or is_atom(currency)) and is_integer(amount) do
-      case Money.new(currency, amount, params) do
-        %Money{} = money -> {:ok, money}
-        {:error, {exception, message}} -> {:error, exception: exception, message: message}
-      end
-    end
-
-    def cast(%{"currency" => currency, "amount" => amount}, params)
-        when (is_binary(currency) or is_atom(currency)) and is_binary(amount) do
-      case Money.new(currency, amount, params) do
-        %Money{} = money -> {:ok, money}
-        {:error, {exception, message}} -> {:error, exception: exception, message: message}
-      end
-    end
-
-    def cast(%{"currency" => currency, "amount" => %Decimal{} = amount}, params)
-        when is_binary(currency) or is_atom(currency) do
-      case Money.new(currency, amount, params) do
-        %Money{} = money -> {:ok, money}
-        {:error, {exception, message}} -> {:error, exception: exception, message: message}
-      end
+        when (is_binary(currency) or is_atom(currency)) and
+               (is_integer(amount) or is_binary(amount) or is_struct(amount, Decimal)) do
+      currency
+      |> Money.new(amount, params)
+      |> cast_result()
     end
 
     def cast(%{currency: currency, amount: amount}, params) do
@@ -217,16 +201,25 @@ if Code.ensure_loaded?(Ecto.Type) do
     end
 
     def cast(string, params) when is_binary(string) do
-      case Money.parse(string, params) do
-        {:error, {exception, message}} -> {:error, exception: exception, message: message}
-        money -> {:ok, money}
-      end
+      string
+      |> Money.parse(params)
+      |> cast_result()
     end
 
     def cast(_money, _params) do
       :error
     end
 
+    # Money returns `{:error, {module, message}}` for its own errors and
+    # `{:error, exception}` for errors from Localize, such as an invalid locale.
+    defp cast_result(%Money{} = money), do: {:ok, money}
+
+    defp cast_result({:error, {exception, message}}),
+      do: {:error, exception: exception, message: message}
+
+    defp cast_result({:error, exception}) when is_exception(exception),
+      do: {:error, exception: exception.__struct__, message: Exception.message(exception)}
+
     # embed_as is set to :dump because if it is set to
     # `:self` then `cast/2` will be called when loading. And
     # since casting is locale-sensitive, the results may
diff --git a/test/money_ecto_edge_case_test.exs b/test/money_ecto_edge_case_test.exs
index 70124f6..dc25f2d 100644
--- a/test/money_ecto_edge_case_test.exs
+++ b/test/money_ecto_edge_case_test.exs
@@ -70,6 +70,27 @@ defmodule Money.Ecto.EdgeCaseTest do
       assert Composite.cast(nil, @params) == {:ok, nil}
       assert Composite.cast(42, @params) == :error
     end
+
+    test "an invalid locale is a cast error for \"100 CHF\" and a CHF 100 map" do
+      params = Composite.init(locale: "!invalid!")
+
+      for type <- [Composite, Map],
+          input <- [
+            "100 CHF",
+            %{"currency" => "CHF", "amount" => "100"},
+            %{currency: :CHF, amount: "100"}
+          ] do
+        assert {:error, exception: Localize.InvalidLocaleError, message: message} =
+                 type.cast(input, params)
+
+        assert message =~ "!invalid!"
+      end
+    end
+
+    test "an unknown currency XYZ is still a cast error" do
+      assert {:error, exception: Money.UnknownCurrencyError, message: _} =
+               Composite.cast(%{"currency" => "XYZ", "amount" => "1"}, @params)
+    end
   end
 
   describe "composite type equality and embedding" do