diff --git a/src/mergeProps.ts b/src/mergeProps.ts
index 22e2ecb..58edd9b 100644
--- a/src/mergeProps.ts
+++ b/src/mergeProps.ts
@@ -6,20 +6,23 @@ import { isJSONSchemaObjectType } from './utils';
 /**
  * Merge and dedupe 2 tuples
  */
-type MergeTuples<T1, T2> = readonly [
-  ...UnionToTuple<TupleToUnion<T1> | TupleToUnion<T2>>,
-];
+type MergeTuples<T1, T2> = Readonly<
+  UnionToTuple<TupleToUnion<T1> | TupleToUnion<T2>>
+>;
 
+/**
+ * Merge two optional records, keeping `undefined` if both are undefined
+ */
 type MergeOptionalRecords<
-  Object1 extends Record<string, unknown> | undefined,
-  Object2 extends Record<string, unknown> | undefined,
+  A extends Record<string, unknown> | undefined,
+  B extends Record<string, unknown> | undefined,
 > =
-  Object1 extends Record<string, unknown>
-    ? Object2 extends Record<string, unknown>
-      ? Merge<Object1, Object2>
-      : Object1
-    : Object2 extends Record<string, unknown>
-      ? Object2
+  A extends Record<string, unknown>
+    ? B extends Record<string, unknown>
+      ? Merge<A, B>
+      : A
+    : B extends Record<string, unknown>
+      ? B
       : undefined;
 
 type MergeProps<
diff --git a/src/omitProps.ts b/src/omitProps.ts
index bbcb0d0..f5e8d52 100644
--- a/src/omitProps.ts
+++ b/src/omitProps.ts
@@ -1,12 +1,12 @@
-import type { Merge, SetRequired, TupleToUnion, UnionToTuple } from 'type-fest';
+import type { Merge, SetRequired } from 'type-fest';
 
-import type { JSONSchemaObject, JSONSchemaObjectOutput } from './types';
+import type {
+  JSONSchemaObject,
+  JSONSchemaObjectOutput,
+  OmitFromTuple,
+} from './types';
 import { isJSONSchemaObjectType } from './utils';
 
-type OmitFromTuple<Tuple extends readonly unknown[], EntriesToOmit> = Readonly<
-  UnionToTuple<Exclude<TupleToUnion<Tuple>, EntriesToOmit>>
->;
-
 type OmitSchemaProperties<
   Schema extends JSONSchemaObject,
   Keys extends (keyof Schema['properties'])[],
@@ -16,11 +16,7 @@ type OmitSchemaProperties<
     properties: Omit<Schema['properties'], Keys[number]>;
     required: undefined extends Schema['required']
       ? undefined
-      : OmitFromTuple<
-          // @ts-expect-error extends doesn't narrow type
-          Schema['required'],
-          Keys[number]
-        >;
+      : OmitFromTuple<Schema['required'], Keys[number]>;
   }
 >;
 
diff --git a/src/optionalProps.ts b/src/optionalProps.ts
index e1f851d..292949a 100644
--- a/src/optionalProps.ts
+++ b/src/optionalProps.ts
@@ -1,6 +1,10 @@
-import type { Merge, TupleToUnion, UnionToTuple } from 'type-fest';
+import type { Merge } from 'type-fest';
 
-import type { JSONSchemaObject, JSONSchemaObjectOutput } from './types';
+import type {
+  JSONSchemaObject,
+  JSONSchemaObjectOutput,
+  OmitFromTuple,
+} from './types';
 import { isJSONSchemaObjectType } from './utils';
 
 type ObjectKeys = string | number | symbol;
@@ -15,11 +19,7 @@ type OptionalProps<
     Merge<
       Schema,
       {
-        required: Readonly<
-          UnionToTuple<
-            Exclude<TupleToUnion<Schema['required']>, TupleToUnion<Keys>>
-          >
-        >;
+        required: OmitFromTuple<Schema['required'], NonNullable<Keys>[number]>;
       }
     >;
 /**
diff --git a/src/sealSchema.ts b/src/sealSchema.ts
index e78fe86..68fc416 100644
--- a/src/sealSchema.ts
+++ b/src/sealSchema.ts
@@ -3,21 +3,23 @@ import type { Merge } from 'type-fest';
 import type { JSONSchema, JSONSchemaObjectOutput } from './types';
 import { isObject } from './utils';
 
-type DisableAdditionalProperties<Value extends object> =
-  'type' extends keyof Value
-    ? Value['type'] extends 'object'
-      ? Merge<Value, Readonly<{ additionalProperties: false }>>
-      : Value
-    : Value;
-
-type DisableAdditionalPropertiesDeep<
-  _Value extends object,
-  Value = DisableAdditionalProperties<_Value>,
-> = {
-  [Key in keyof Value]: Value[Key] extends object
-    ? DisableAdditionalPropertiesDeep<Value[Key]>
-    : Value[Key];
-};
+type DisableAdditionalPropertiesDeep<Value> = Value extends object
+  ? Value extends { type: 'object' }
+    ? // JSON schema object type
+      Readonly<
+        Merge<
+          {
+            [Key in keyof Value]: DisableAdditionalPropertiesDeep<Value[Key]>;
+          },
+          { additionalProperties: false }
+        >
+      >
+    : // Any other object/array
+      Readonly<{
+        [Key in keyof Value]: DisableAdditionalPropertiesDeep<Value[Key]>;
+      }>
+  : // Any other primitive
+    Value;
 
 function disableAdditionalPropertiesDeep(item: unknown): unknown {
   if (isObject(item)) {
diff --git a/src/types.ts b/src/types.ts
index 92afe06..7de389e 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -3,6 +3,8 @@ import type {
   OverrideProperties,
   SetRequired,
   Simplify,
+  TupleToUnion,
+  UnionToTuple,
 } from 'type-fest';
 
 // https://github.com/ThomasAribart/json-schema-to-ts/blob/12767c1eab895159c01f5e6898d8e5e711ff9d1c/src/definitions/jsonSchema.ts
@@ -27,3 +29,8 @@ export type JSONSchemaObjectOutput<Schema> = Simplify<
     ConditionalExcept<Schema, readonly [] | undefined>
   >
 >;
+
+export type OmitFromTuple<
+  Tuple extends readonly unknown[] | undefined,
+  EntriesToOmit,
+> = Readonly<UnionToTuple<Exclude<TupleToUnion<Tuple>, EntriesToOmit>>>;
diff --git a/src/unsealSchema.ts b/src/unsealSchema.ts
index 8ed963a..76c4908 100644
--- a/src/unsealSchema.ts
+++ b/src/unsealSchema.ts
@@ -1,20 +1,21 @@
 import type { JSONSchema, JSONSchemaObjectOutput } from './types';
 import { isObject } from './utils';
 
-type OmitAdditionalProperty<Value extends object> = 'type' extends keyof Value
-  ? Value['type'] extends 'object'
-    ? Omit<Value, 'additionalProperties'>
-    : Value
-  : Value;
-
-type OmitAdditionalPropertiesDeep<
-  _Value extends object,
-  Value = OmitAdditionalProperty<_Value>,
-> = {
-  [Key in keyof Value]: Value[Key] extends object
-    ? OmitAdditionalPropertiesDeep<Value[Key]>
-    : Value[Key];
-};
+type OmitAdditionalPropertiesDeep<Value> = Value extends object
+  ? Value extends { type: 'object' }
+    ? // JSON schema object type
+      Readonly<{
+        [Key in keyof Omit<
+          Value,
+          'additionalProperties'
+        >]: OmitAdditionalPropertiesDeep<Value[Key]>;
+      }>
+    : // Any other object/array
+      Readonly<{
+        [Key in keyof Value]: OmitAdditionalPropertiesDeep<Value[Key]>;
+      }>
+  : // Any other primitive
+    Value;
 
 function omitAdditionalPropertiesDeep(item: unknown): unknown {
   if (isObject(item)) {
diff --git a/tsconfig.json b/tsconfig.json
index 32fd101..9530956 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -4,7 +4,8 @@
     "isolatedModules": true,
     "erasableSyntaxOnly": true,
     "noUncheckedIndexedAccess": true,
-    "noImplicitOverride": true
+    "noImplicitOverride": true,
+    "noErrorTruncation": true
   },
   "exclude": ["./dist"]
 }