diff --git a/__tests__/produce.ts b/__tests__/produce.ts
index e034a8a9..1c8a14a0 100644
--- a/__tests__/produce.ts
+++ b/__tests__/produce.ts
@@ -769,3 +769,17 @@ it("infers async curried", async () => {
 		assert(n, _ as ROState) // yay!
 	}
 }
+
+it("allows for mixed property value types", () => {
+	type TestReadonlyObject = {
+		readonly testObjectOrNull: {readonly testProperty: number} | null
+	}
+
+	const input: TestReadonlyObject = {testObjectOrNull: null}
+
+	produce(input, draft => {
+		if (draft.testObjectOrNull) {
+			draft.testObjectOrNull.testProperty = 5
+		}
+	})
+})
diff --git a/__tests__/types/type-externals.ts b/__tests__/types/type-externals.ts
deleted file mode 100644
index 0cf9a4c8..00000000
--- a/__tests__/types/type-externals.ts
+++ /dev/null
@@ -1,9 +0,0 @@
-import {isType, JSONTypes} from "type-plus"
-import {Draft} from "../../src/types/types-external"
-
-describe("Draft<T>", () => {
-	test("can use JSONTypes as T", () => {
-		type A = Draft<JSONTypes>
-		isType.equal<true, JSONTypes, A>()
-	})
-})
diff --git a/package.json b/package.json
index 84e30237..4775980f 100644
--- a/package.json
+++ b/package.json
@@ -99,7 +99,6 @@
     "spec.ts": "^1.1.0",
     "ts-jest": "^25.2.0",
     "tsdx": "^0.12.3",
-    "type-plus": "^4.15.2",
     "typescript": "^4.2.3"
   }
 }
diff --git a/src/types/types-external.ts b/src/types/types-external.ts
index 2bf551ec..d1ef6482 100644
--- a/src/types/types-external.ts
+++ b/src/types/types-external.ts
@@ -30,9 +30,7 @@ export type IfAvailable<T, Fallback = void> =
  */
 type WeakReferences = IfAvailable<WeakMap<any, any>> | IfAvailable<WeakSet<any>>
 
-export type WritableDraft<T> = {
-	-readonly [K in keyof T]: T[K] extends object ? Draft<T[K]> : T[K]
-}
+export type WritableDraft<T> = {-readonly [K in keyof T]: Draft<T[K]>}
 
 /** Convert a readonly type into a mutable type, if possible */
 export type Draft<T> = T extends PrimitiveType
diff --git a/yarn.lock b/yarn.lock
index 5b75262e..ef9d82db 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1791,11 +1791,6 @@ acorn@^7.1.0:
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-7.1.0.tgz#949d36f2c292535da602283586c2477c57eb2d6c"
   integrity sha512-kL5CuoXA/dgxlBbVrflsflzQ3PAas7RYZB52NOm/6839iVYJgKMJ3cQJD+t2i5+qFa8h3MDpEOJiS64E8JLnSQ==
 
-acorn@^8.8.0:
-  version "8.8.1"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-8.8.1.tgz#0a3f9cbecc4ec3bea6f0a80b66ae8dd2da250b73"
-  integrity sha512-7zFpHzhnqYKrkYdUjF1HI1bzd0VygEGX8lFk4k5zVMqHEoES+P+7TKI+EvLO9WVMJ8eekdO0aDEK044xTXwPPA==
-
 agent-base@4, agent-base@^4.3.0:
   version "4.3.0"
   resolved "https://registry.yarnpkg.com/agent-base/-/agent-base-4.3.0.tgz#8165f01c436009bccad0b1d122f05ed770efc6ee"
@@ -5859,11 +5854,6 @@ is-buffer@^1.1.5:
   resolved "https://registry.yarnpkg.com/is-buffer/-/is-buffer-1.1.6.tgz#efaa2ea9daa0d7ab2ea13a97b2b8ad51fefbe8be"
   integrity sha512-NcdALwpXkTm5Zvvbk7owOUSvVvBKDgKP5/ewfXEznmQFfs4ZRmanOeKBTjRVjka3QFoN6XJ+9F3USqfHqTaU5w==
 
-is-buffer@^2.0.5:
-  version "2.0.5"
-  resolved "https://registry.yarnpkg.com/is-buffer/-/is-buffer-2.0.5.tgz#ebc252e400d22ff8d77fa09888821a24a658c191"
-  integrity sha512-i2R6zNFDwgEHJyQUtJEk0XFi1i0dPFn/oqjK3/vPCcDeJvW5NQ83V8QbicfF1SupOaB0h8ntgBC2YiE7dfyctQ==
-
 is-callable@^1.1.4, is-callable@^1.2.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/is-callable/-/is-callable-1.2.0.tgz#83336560b54a38e35e3a2df7afd0454d691468bb"
@@ -11265,15 +11255,6 @@ terser@^4.1.2, terser@^4.6.2:
     source-map "~0.6.1"
     source-map-support "~0.5.12"
 
-tersify@^3.10.2:
-  version "3.10.5"
-  resolved "https://registry.yarnpkg.com/tersify/-/tersify-3.10.5.tgz#eb2b230e7725481129b7fa349f2ce2683bd8a9ec"
-  integrity sha512-dLgsTbGVH/6Z+KU4d+NqMmsMFRwRmTFNxsl5vKGkUmaSQ0TTAwnv+Hck5S8Pdn5bcZSyjR3aTvvetJ7ZUs+ZYg==
-  dependencies:
-    acorn "^8.8.0"
-    is-buffer "^2.0.5"
-    unpartial "^1.0.0"
-
 test-exclude@^5.2.3:
   version "5.2.3"
   resolved "https://registry.yarnpkg.com/test-exclude/-/test-exclude-5.2.3.tgz#c3d3e1e311eb7ee405e092dac10aefd09091eac0"
@@ -11626,14 +11607,6 @@ type-fest@^0.8.1:
   resolved "https://registry.yarnpkg.com/type-fest/-/type-fest-0.8.1.tgz#09e249ebde851d3b1e48d27c105444667f17b83d"
   integrity sha512-4dbzIzqvjtgiM5rw1k5rEHtBANKmdudhGyBEajN01fEyhaAIhsoKNy6y7+IN93IfpFtwY9iqi7kD+xwKhQsNJA==
 
-type-plus@^4.15.2:
-  version "4.15.2"
-  resolved "https://registry.yarnpkg.com/type-plus/-/type-plus-4.15.2.tgz#2d97273bde0c921845ae70a0d1cef075a7c0cfc1"
-  integrity sha512-5hEzFXMHOK/p5hVhNmgy7CIxUjTIK9a/NOw0pDbc4tb7LXm9JLwLEH0QdGWU5fGPp5l05rtPZfjdSOPqfAyX9w==
-  dependencies:
-    tersify "^3.10.2"
-    unpartial "^1.0.3"
-
 typedarray-to-buffer@^3.1.5:
   version "3.1.5"
   resolved "https://registry.yarnpkg.com/typedarray-to-buffer/-/typedarray-to-buffer-3.1.5.tgz#a97ee7a9ff42691b9f783ff1bc5112fe3fca9080"
@@ -11752,11 +11725,6 @@ universalify@^2.0.0:
   resolved "https://registry.yarnpkg.com/universalify/-/universalify-2.0.0.tgz#75a4984efedc4b08975c5aeb73f530d02df25717"
   integrity sha512-hAZsKq7Yy11Zu1DE0OzWjw7nnLZmJZYTDZZyEFHZdUhV8FkH5MCfoU1XMaxXovpyW5nq5scPqq0ZDP9Zyl04oQ==
 
-unpartial@^1.0.0, unpartial@^1.0.3:
-  version "1.0.4"
-  resolved "https://registry.yarnpkg.com/unpartial/-/unpartial-1.0.4.tgz#56490ed475105110cee61890a80c5da394741833"
-  integrity sha512-xY8319WOQcRDRVFWvTty2YJXKvM8XRPehqWZUd7k/BatpbuitI4Jd+2xlwjTZbZScSvT75TnUsUmy5uwFa3o0g==
-
 unpipe@~1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/unpipe/-/unpipe-1.0.0.tgz#b2bf4ee8514aae6165b4817829d21b2ef49904ec"