diff --git a/lib/open_api/open_api.ex b/lib/open_api/open_api.ex
index e2895e8..ad11174 100644
--- a/lib/open_api/open_api.ex
+++ b/lib/open_api/open_api.ex
@@ -101,7 +101,7 @@ defmodule EctoCommand.OpenApi do
         |> Map.put(:exclusiveMaximum, false)
 
       {:not_equal_to, value}, acc ->
-        Map.put(acc, :not, %{enum: [value]})
+        Map.put(acc, :not, %OpenApiSpex.Schema{enum: [value]})
     end)
   end
 
diff --git a/test/unit/command/open_api/open_api_test.exs b/test/unit/command/open_api/open_api_test.exs
index b6af55b..20df552 100644
--- a/test/unit/command/open_api/open_api_test.exs
+++ b/test/unit/command/open_api/open_api_test.exs
@@ -59,7 +59,7 @@ defmodule Unit.EctoCommand.OpenApi.OpenApiTest do
                type: :integer,
                example: 20
              },
-             an_integer_b: %OpenApiSpex.Schema{type: :integer, not: %{enum: [20]}, example: 21},
+             an_integer_b: %OpenApiSpex.Schema{type: :integer, not: %OpenApiSpex.Schema{enum: [20]}, example: 21},
              an_integer_c: %OpenApiSpex.Schema{
                exclusiveMaximum: false,
                exclusiveMinimum: true,