diff --git a/ts-types/array-length/ensure.d.ts b/ts-types/array-length/ensure.d.ts
index 7c15760..a60a0f5 100644
--- a/ts-types/array-length/ensure.d.ts
+++ b/ts-types/array-length/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureArrayLength(value: any, options?: EnsureBaseOptions & EnsureIsOptional): number | null;
+declare function ensureArrayLength(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<number>): number;
 
-declare function ensureArrayLength(value: any, options?: EnsureOptions): number;
 export default ensureArrayLength;
diff --git a/ts-types/array-like/ensure.d.ts b/ts-types/array-like/ensure.d.ts
index df60e90..299caaa 100644
--- a/ts-types/array-like/ensure.d.ts
+++ b/ts-types/array-like/ensure.d.ts
@@ -1,7 +1,10 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
 
 type LengthwiseObject = { length: number } & object;
-type ArrayLikeEnsureOptions = { allowString?: boolean } | EnsureOptions;
+type ArrayLikeEnsureOptions = { allowString?: boolean };
+
+
+declare function ensureArrayLike<T>(value: any, options?: ArrayLikeEnsureOptions & EnsureBaseOptions & EnsureIsOptional): T[] | string | LengthwiseObject | null;
+declare function ensureArrayLike<T>(value: any, options?: ArrayLikeEnsureOptions & EnsureBaseOptions & EnsureIsOptional & EnsureDefault<T[] | string | LengthwiseObject>): T[] | string | LengthwiseObject;
 
-declare function ensureArrayLike<T>(value: any, options?: ArrayLikeEnsureOptions): T[] | string | LengthwiseObject;
 export default ensureArrayLike;
diff --git a/ts-types/array/ensure.d.ts b/ts-types/array/ensure.d.ts
index a6b162d..cf8f31a 100644
--- a/ts-types/array/ensure.d.ts
+++ b/ts-types/array/ensure.d.ts
@@ -1,6 +1,9 @@
-import { EnsureFunction, EnsureOptions } from '../ensure';
+import { EnsureFunction,  EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
 
-type EnsureArrayOptions = { ensureItem?: EnsureFunction } | EnsureOptions;
+type EnsureArrayOptions = { ensureItem?: EnsureFunction };
+
+
+declare function ensureArray<T>(value: any, options?: EnsureArrayOptions & EnsureBaseOptions & EnsureIsOptional): T[] | null;
+declare function ensureArray<T>(value: any, options?: EnsureArrayOptions & EnsureBaseOptions & EnsureIsOptional & EnsureDefault<T[]>): T[];
 
-declare function ensureArray<T>(value: any, options?: EnsureArrayOptions): T[];
 export default ensureArray;
diff --git a/ts-types/big-int/ensure.d.ts b/ts-types/big-int/ensure.d.ts
index de960b0..9c6b4a8 100644
--- a/ts-types/big-int/ensure.d.ts
+++ b/ts-types/big-int/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from "../ensure";
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureBigInt(value: any, options?: EnsureBaseOptions & EnsureIsOptional): bigint | null;
+declare function ensureBigInt(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<bigint>): bigint;
 
-declare function ensureBigInt(value: any, options?: EnsureOptions): bigint;
 export default ensureBigInt;
diff --git a/ts-types/constructor/ensure.d.ts b/ts-types/constructor/ensure.d.ts
index ff215a8..cecc8e8 100644
--- a/ts-types/constructor/ensure.d.ts
+++ b/ts-types/constructor/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureFunction, EnsureOptions } from '../ensure';
+import { EnsureFunction, EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureConstructor(value: any, options?: EnsureBaseOptions & EnsureIsOptional): EnsureFunction | object | null;
+declare function ensureConstructor(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<EnsureFunction | object>): EnsureFunction | object;
 
-declare function ensureConstructor(value: any, options?: EnsureOptions): EnsureFunction | object;
 export default ensureConstructor;
diff --git a/ts-types/date/ensure.d.ts b/ts-types/date/ensure.d.ts
index 333ceb9..3768b81 100644
--- a/ts-types/date/ensure.d.ts
+++ b/ts-types/date/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureDate(value: any, options?: EnsureBaseOptions & EnsureIsOptional): Date | null;
+declare function ensureDate(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<Date>): Date;
 
-declare function ensureDate(value: any, options?: EnsureOptions): Date;
 export default ensureDate;
diff --git a/ts-types/ensure.d.ts b/ts-types/ensure.d.ts
index bc649dd..fb08efd 100644
--- a/ts-types/ensure.d.ts
+++ b/ts-types/ensure.d.ts
@@ -1,13 +1,21 @@
 export type EnsureFunction = (...args: any[]) => any;
-export interface EnsureOptions {
+export interface EnsureBaseOptions {
 	name?: string;
-	isOptional?: boolean;
-	default?: any;
 	errorMessage?: string;
 	errorCode?: number;
 	Error?: ErrorConstructor;
 }
 
+export interface EnsureIsOptional {
+	isOptional?: boolean;
+}
+
+export interface EnsureDefault<T> {
+	default?: T;
+}
+
+type EnsureOptions = EnsureBaseOptions & EnsureIsOptional & EnsureDefault<any>;
+
 type ValidationDatum = [argumentName: string, inputValue: any, ensureFunction: EnsureFunction, options?: object];
 type ValidationDatumList = ValidationDatum[];
 
diff --git a/ts-types/error/ensure.d.ts b/ts-types/error/ensure.d.ts
index 61f2d70..4b3ba77 100644
--- a/ts-types/error/ensure.d.ts
+++ b/ts-types/error/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureError(value: any, options?: EnsureBaseOptions & EnsureIsOptional): Error | null;
+declare function ensureError(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<Error>): Error;
 
-declare function ensureError(value: any, options?: EnsureOptions): Error;
 export default ensureError;
diff --git a/ts-types/finite/ensure.d.ts b/ts-types/finite/ensure.d.ts
index df37439..3df187b 100644
--- a/ts-types/finite/ensure.d.ts
+++ b/ts-types/finite/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureFinite(value: any, options?: EnsureBaseOptions & EnsureIsOptional): number | null;
+declare function ensureFinite(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<number>): number;
 
-declare function ensureFinite(value: any, options?: EnsureOptions): number;
 export default ensureFinite;
diff --git a/ts-types/function/ensure.d.ts b/ts-types/function/ensure.d.ts
index 758d3ea..20bb430 100644
--- a/ts-types/function/ensure.d.ts
+++ b/ts-types/function/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureFunction, EnsureOptions } from '../ensure';
+import { EnsureFunction, EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureFunction(value: any, options?: EnsureBaseOptions & EnsureIsOptional): EnsureFunction | null;
+declare function ensureFunction(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<EnsureFunction>): EnsureFunction;
 
-declare function ensureFunction(value: any, options?: EnsureOptions): EnsureFunction;
 export default ensureFunction;
diff --git a/ts-types/integer/ensure.d.ts b/ts-types/integer/ensure.d.ts
index d02c939..2bf4548 100644
--- a/ts-types/integer/ensure.d.ts
+++ b/ts-types/integer/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureInteger(value: any, options?: EnsureBaseOptions & EnsureIsOptional): number | null;
+declare function ensureInteger(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<number>): number;
 
-declare function ensureInteger(value: any, options?: EnsureOptions): number;
 export default ensureInteger;
diff --git a/ts-types/iterable/ensure.d.ts b/ts-types/iterable/ensure.d.ts
index d122487..fd3bce6 100644
--- a/ts-types/iterable/ensure.d.ts
+++ b/ts-types/iterable/ensure.d.ts
@@ -1,6 +1,9 @@
-import { EnsureFunction, EnsureOptions } from '../ensure';
+import { EnsureFunction, EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
 
-type IterableEnsureOptions = { ensureItem?: EnsureFunction, allowString?: boolean, denyEmpty?: boolean} | EnsureOptions;
+type IterableEnsureOptions = { ensureItem?: EnsureFunction, allowString?: boolean, denyEmpty?: boolean};
+
+
+declare function ensureIterable<T>(value: any, options?: IterableEnsureOptions & EnsureBaseOptions & EnsureIsOptional): T[] | null;
+declare function ensureIterable<T>(value: any, options?: IterableEnsureOptions & EnsureBaseOptions & EnsureIsOptional & EnsureDefault<T[]>): T[];
 
-declare function ensureIterable<T>(value: any, options?: IterableEnsureOptions): T[];
 export default ensureIterable;
diff --git a/ts-types/map/ensure.d.ts b/ts-types/map/ensure.d.ts
index 3bb171d..a03a7e8 100644
--- a/ts-types/map/ensure.d.ts
+++ b/ts-types/map/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureMap<K, V>(value: any, options?: EnsureBaseOptions & EnsureIsOptional): Map<K, V> | null;
+declare function ensureMap<K, V>(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<Map<K, V>>): Map<K, V>;
 
-declare function ensureMap<K, V>(value: any, options?: EnsureOptions): Map<K, V>;
 export default ensureMap;
diff --git a/ts-types/natural-number/ensure.d.ts b/ts-types/natural-number/ensure.d.ts
index 4f9676e..18b1547 100644
--- a/ts-types/natural-number/ensure.d.ts
+++ b/ts-types/natural-number/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureNaturalNumber(value: any, options?: EnsureBaseOptions & EnsureIsOptional): number | null;
+declare function ensureNaturalNumber(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<number>): number;
 
-declare function ensureNaturalNumber(value: any, options?: EnsureOptions): number;
 export default ensureNaturalNumber;
diff --git a/ts-types/number/ensure.d.ts b/ts-types/number/ensure.d.ts
index b25d505..88ed75f 100644
--- a/ts-types/number/ensure.d.ts
+++ b/ts-types/number/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureNumber(value: any, options?: EnsureBaseOptions & EnsureIsOptional): number | null;
+declare function ensureNumber(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<number>): number;
 
-declare function ensureNumber(value: any, options?: EnsureOptions): number;
 export default ensureNumber;
diff --git a/ts-types/object/ensure.d.ts b/ts-types/object/ensure.d.ts
index 8ad8b91..d15cc80 100644
--- a/ts-types/object/ensure.d.ts
+++ b/ts-types/object/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureObject(value: any, options?: EnsureBaseOptions & EnsureIsOptional): object | null;
+declare function ensureObject(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<object>): object;
 
-declare function ensureObject(value: any, options?: EnsureOptions): object;
 export default ensureObject;
diff --git a/ts-types/plain-function/ensure.d.ts b/ts-types/plain-function/ensure.d.ts
index 8f7d878..0017d65 100644
--- a/ts-types/plain-function/ensure.d.ts
+++ b/ts-types/plain-function/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureFunction, EnsureOptions } from '../ensure';
+import { EnsureFunction, EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensurePlainFunction(value: any, options?: EnsureBaseOptions & EnsureIsOptional): EnsureFunction | null;
+declare function ensurePlainFunction(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<EnsureFunction>): EnsureFunction;
 
-declare function ensurePlainFunction(value: any, options?: EnsureOptions): EnsureFunction;
 export default ensurePlainFunction;
diff --git a/ts-types/plain-object/ensure.d.ts b/ts-types/plain-object/ensure.d.ts
index 6b7e646..a9e7bcc 100644
--- a/ts-types/plain-object/ensure.d.ts
+++ b/ts-types/plain-object/ensure.d.ts
@@ -1,6 +1,9 @@
-import { EnsureFunction, EnsureOptions } from '../ensure';
+import { EnsureFunction, EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
 
-type PlainObjectEnsureOptions = {allowedKeys?: string[], ensurePropertyValue?: EnsureFunction} | EnsureOptions;
+type PlainObjectEnsureOptions = {allowedKeys?: string[], ensurePropertyValue?: EnsureFunction};
+
+
+declare function ensurePlainObject(value: any, options?: PlainObjectEnsureOptions & EnsureBaseOptions & EnsureIsOptional): object | null;
+declare function ensurePlainObject(value: any, options?: PlainObjectEnsureOptions & EnsureBaseOptions & EnsureIsOptional & EnsureDefault<object>): object;
 
-declare function ensurePlainObject(value: any, options?: PlainObjectEnsureOptions): object;
 export default ensurePlainObject;
diff --git a/ts-types/promise/ensure.d.ts b/ts-types/promise/ensure.d.ts
index 4e4f1a9..6097c9c 100644
--- a/ts-types/promise/ensure.d.ts
+++ b/ts-types/promise/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensurePromise<T>(value: any, options?: EnsureBaseOptions & EnsureIsOptional): Promise<T> | null;
+declare function ensurePromise<T>(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<Promise<T>>): Promise<T>;
 
-declare function ensurePromise<T>(value: any, options?: EnsureOptions): Promise<T>;
 export default ensurePromise;
diff --git a/ts-types/reg-exp/ensure.d.ts b/ts-types/reg-exp/ensure.d.ts
index e9dbcdb..85a4192 100644
--- a/ts-types/reg-exp/ensure.d.ts
+++ b/ts-types/reg-exp/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureRegExp(value: any, options?: EnsureBaseOptions & EnsureIsOptional): RegExp | null;
+declare function ensureRegExp(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<RegExp>): RegExp;
 
-declare function ensureRegExp(value: any, options?: EnsureOptions): RegExp;
 export default ensureRegExp;
diff --git a/ts-types/safe-integer/ensure.d.ts b/ts-types/safe-integer/ensure.d.ts
index 646d13e..5b1fdd6 100644
--- a/ts-types/safe-integer/ensure.d.ts
+++ b/ts-types/safe-integer/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureSafeInteger(value: any, options?: EnsureBaseOptions & EnsureIsOptional): number | null;
+declare function ensureSafeInteger(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<number>): number;
 
-declare function ensureSafeInteger(value: any, options?: EnsureOptions): number;
 export default ensureSafeInteger;
diff --git a/ts-types/set/ensure.d.ts b/ts-types/set/ensure.d.ts
index 57c152e..d6a2311 100644
--- a/ts-types/set/ensure.d.ts
+++ b/ts-types/set/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureSet<T>(value: any, options?: EnsureBaseOptions & EnsureIsOptional): Set<T> | null;
+declare function ensureSet<T>(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<Set<T>>): Set<T>;
 
-declare function ensureSet<T>(value: any, options?: EnsureOptions): Set<T>;
 export default ensureSet;
diff --git a/ts-types/string/ensure.d.ts b/ts-types/string/ensure.d.ts
index b50013d..06288ef 100644
--- a/ts-types/string/ensure.d.ts
+++ b/ts-types/string/ensure.d.ts
@@ -1,4 +1,6 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
+declare function ensureString(value: any, options?: EnsureBaseOptions & EnsureIsOptional): string | null;
+declare function ensureString(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<string>): string;
 
-declare function ensureString(value: any, options?: EnsureOptions): string;
 export default ensureString;
diff --git a/ts-types/thenable/ensure.d.ts b/ts-types/thenable/ensure.d.ts
index c1604db..3a96577 100644
--- a/ts-types/thenable/ensure.d.ts
+++ b/ts-types/thenable/ensure.d.ts
@@ -1,5 +1,9 @@
-import { EnsureFunction, EnsureOptions } from '../ensure';
+import { EnsureFunction, EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
+
 type ThenableObject = { then: EnsureFunction } & object;
 
-declare function ensureThenable<T>(value: any, options?: EnsureOptions): Promise<T> | ThenableObject;
+
+declare function ensureThenable<T>(value: any, options?: EnsureBaseOptions & EnsureIsOptional): Promise<T> | ThenableObject | null;
+declare function ensureThenable<T>(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<Promise<T> | ThenableObject>): Promise<T> | ThenableObject;
+
 export default ensureThenable;
diff --git a/ts-types/time-value/ensure.d.ts b/ts-types/time-value/ensure.d.ts
index 2beb9b3..f8084b8 100644
--- a/ts-types/time-value/ensure.d.ts
+++ b/ts-types/time-value/ensure.d.ts
@@ -1,4 +1,5 @@
-import { EnsureOptions } from '../ensure';
+import { EnsureBaseOptions, EnsureIsOptional, EnsureDefault } from '../ensure';
 
-declare function ensureTimeValue(value: any, options?: EnsureOptions): number;
+declare function ensureTimeValue(value: any, options?: EnsureBaseOptions & EnsureIsOptional): number | null;
+declare function ensureTimeValue(value: any, options?: EnsureBaseOptions & EnsureIsOptional & EnsureDefault<number>): number;
 export default ensureTimeValue;