diff --git a/CHANGELOG.md b/CHANGELOG.md
index 59b3638657..aeded1fd21 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -366,6 +366,14 @@ for the list of changes made since `v2.0.0-alpha.1`.
 
 - **BREAKING**: The Bower & UMD/CDN package versions are no longer supported.
 
+- **BREAKING**: `null` now is not a valid date. `isValid(null)` returns `false`;
+  `toDate(null)` returns an invalid date. Since `toDate` is used internally
+  by all the functions, operations over `null` will also return an invalid date.
+  [See #537](https://github.com/date-fns/date-fns/issues/537) for the reasoning.
+
+- `toDate` (previously `parse`) and `isValid` functions now accept `any` type
+  as the first argument.
+
 ## [1.28.5] - 2017-05-19
 
 ### Fixed
diff --git a/src/fp/isValid/index.js.flow b/src/fp/isValid/index.js.flow
index aa98db831a..60e11ab7b5 100644
--- a/src/fp/isValid/index.js.flow
+++ b/src/fp/isValid/index.js.flow
@@ -63,4 +63,4 @@ type CurriedFn4<A, B, C, D, R> = <A>(a: A) => CurriedFn3<B, C, D, R>
   | <A,B,C>(a: A, b: B, c: C) => CurriedFn1<D, R>
   | <A,B,C,D>(a: A, b: B, c: C, d: D) => R
 
-declare module.exports: CurriedFn1<Date | string | number, boolean>
+declare module.exports: CurriedFn1<any, boolean>
diff --git a/src/fp/isValidWithOptions/index.js.flow b/src/fp/isValidWithOptions/index.js.flow
index afcfb6b713..3b17d9b08e 100644
--- a/src/fp/isValidWithOptions/index.js.flow
+++ b/src/fp/isValidWithOptions/index.js.flow
@@ -63,4 +63,4 @@ type CurriedFn4<A, B, C, D, R> = <A>(a: A) => CurriedFn3<B, C, D, R>
   | <A,B,C>(a: A, b: B, c: C) => CurriedFn1<D, R>
   | <A,B,C,D>(a: A, b: B, c: C, d: D) => R
 
-declare module.exports: CurriedFn2<Options, Date | string | number, boolean>
+declare module.exports: CurriedFn2<Options, any, boolean>
diff --git a/src/fp/toDate/index.js.flow b/src/fp/toDate/index.js.flow
index f59bc03899..1e903eb3bb 100644
--- a/src/fp/toDate/index.js.flow
+++ b/src/fp/toDate/index.js.flow
@@ -63,4 +63,4 @@ type CurriedFn4<A, B, C, D, R> = <A>(a: A) => CurriedFn3<B, C, D, R>
   | <A,B,C>(a: A, b: B, c: C) => CurriedFn1<D, R>
   | <A,B,C,D>(a: A, b: B, c: C, d: D) => R
 
-declare module.exports: CurriedFn1<Date | string | number, Date>
+declare module.exports: CurriedFn1<any, Date>
diff --git a/src/fp/toDateWithOptions/index.js.flow b/src/fp/toDateWithOptions/index.js.flow
index ea9a8f1ae8..96674a9f9b 100644
--- a/src/fp/toDateWithOptions/index.js.flow
+++ b/src/fp/toDateWithOptions/index.js.flow
@@ -63,4 +63,4 @@ type CurriedFn4<A, B, C, D, R> = <A>(a: A) => CurriedFn3<B, C, D, R>
   | <A,B,C>(a: A, b: B, c: C) => CurriedFn1<D, R>
   | <A,B,C,D>(a: A, b: B, c: C, d: D) => R
 
-declare module.exports: CurriedFn2<Options, Date | string | number, Date>
+declare module.exports: CurriedFn2<Options, any, Date>
diff --git a/src/isValid/index.js b/src/isValid/index.js
index eff0fc8790..57b9fc6e84 100644
--- a/src/isValid/index.js
+++ b/src/isValid/index.js
@@ -12,7 +12,7 @@ import toDate from '../toDate/index.js'
  *
  * Time value of Date: http://es5.github.io/#x15.9.1.1
  *
- * @param {Date|String|Number} date - the date to check
+ * @param {*} date - the date to check
  * @param {Options} [options] - the object with options. See [Options]{@link https://date-fns.org/docs/Options}
  * @param {0|1|2} [options.additionalDigits=2] - passed to `toDate`. See [toDate]{@link https://date-fns.org/docs/toDate}
  * @returns {Boolean} the date is valid
diff --git a/src/isValid/index.js.flow b/src/isValid/index.js.flow
index b97eaa0b07..a7177efe99 100644
--- a/src/isValid/index.js.flow
+++ b/src/isValid/index.js.flow
@@ -50,6 +50,6 @@ type Locale = {
 }
 
 declare module.exports: (
-  date: Date | string | number,
+  date: any,
   options?: Options
 ) => boolean
diff --git a/src/isValid/test.js b/src/isValid/test.js
index 261c2049ad..40ed1aaea6 100644
--- a/src/isValid/test.js
+++ b/src/isValid/test.js
@@ -25,6 +25,11 @@ describe('isValid', function () {
     assert(isValid(NaN) === false)
   })
 
+  it('treats null as an invalid date', function () {
+    var result = isValid(null)
+    assert(result === false)
+  })
+
   it('throws `RangeError` if `options.additionalDigits` is not convertable to 0, 1, 2 or undefined', function () {
     // $ExpectedMistake
     var block = isValid.bind(null, new Date(), {additionalDigits: NaN})
diff --git a/src/toDate/index.js b/src/toDate/index.js
index c34a29253d..f26e1706e5 100644
--- a/src/toDate/index.js
+++ b/src/toDate/index.js
@@ -54,12 +54,14 @@ var patterns = {
  * Function accepts complete ISO 8601 formats as well as partial implementations.
  * ISO 8601: http://en.wikipedia.org/wiki/ISO_8601
  *
+ * If the argument is null, it is treated as an invalid date.
+ *
  * If all above fails, the function passes the given argument to Date constructor.
  *
  * **Note**: *all* Date arguments passed to any *date-fns* function is processed by `toDate`.
  * All *date-fns* functions will throw `RangeError` if `options.additionalDigits` is not 0, 1, 2 or undefined.
  *
- * @param {Date|String|Number} argument - the value to convert
+ * @param {*} argument - the value to convert
  * @param {Options} [options] - the object with options. See [Options]{@link https://date-fns.org/docs/Options}
  * @param {0|1|2} [options.additionalDigits=2] - the additional number of digits in the extended year format
  * @returns {Date} the parsed date in the local time zone
@@ -82,6 +84,10 @@ export default function toDate (argument, dirtyOptions) {
     throw new TypeError('1 argument required, but only ' + arguments.length + ' present')
   }
 
+  if (argument === null) {
+    return new Date(NaN)
+  }
+
   var options = dirtyOptions || {}
 
   var additionalDigits = options.additionalDigits === undefined ? DEFAULT_ADDITIONAL_DIGITS : Number(options.additionalDigits)
diff --git a/src/toDate/index.js.flow b/src/toDate/index.js.flow
index 8817897f9c..e03b8a4c9d 100644
--- a/src/toDate/index.js.flow
+++ b/src/toDate/index.js.flow
@@ -50,6 +50,6 @@ type Locale = {
 }
 
 declare module.exports: (
-  argument: Date | string | number,
+  argument: any,
   options?: Options
 ) => Date
diff --git a/src/toDate/test.js b/src/toDate/test.js
index 80120b8835..1d14a36495 100644
--- a/src/toDate/test.js
+++ b/src/toDate/test.js
@@ -247,6 +247,12 @@ describe('toDate', function () {
       assert(result instanceof Date)
       assert(isNaN(result))
     })
+
+    it('returns Invalid Date if argument is null', function () {
+      var result = toDate(null)
+      assert(result instanceof Date)
+      assert(isNaN(result))
+    })
   })
 
   it('implicitly converts options', function () {
diff --git a/typings.d.ts b/typings.d.ts
index ee4942857b..6428fcebed 100644
--- a/typings.d.ts
+++ b/typings.d.ts
@@ -650,7 +650,7 @@ declare module 'date-fns' {
   namespace isTuesday {}
 
   function isValid (
-    date: Date | string | number,
+    date: any,
     options?: Options
   ): boolean
   namespace isValid {}
@@ -952,7 +952,7 @@ declare module 'date-fns' {
   namespace subYears {}
 
   function toDate (
-    argument: Date | string | number,
+    argument: any,
     options?: Options
   ): Date
   namespace toDate {}
@@ -3493,10 +3493,10 @@ declare module 'date-fns/fp' {
   const isTuesdayWithOptions: CurriedFn2<Options, Date | string | number, boolean>
   namespace isTuesdayWithOptions {}
 
-  const isValid: CurriedFn1<Date | string | number, boolean>
+  const isValid: CurriedFn1<any, boolean>
   namespace isValid {}
 
-  const isValidWithOptions: CurriedFn2<Options, Date | string | number, boolean>
+  const isValidWithOptions: CurriedFn2<Options, any, boolean>
   namespace isValidWithOptions {}
 
   const isWednesday: CurriedFn1<Date | string | number, boolean>
@@ -3769,10 +3769,10 @@ declare module 'date-fns/fp' {
   const subYearsWithOptions: CurriedFn3<Options, number, Date | string | number, Date>
   namespace subYearsWithOptions {}
 
-  const toDate: CurriedFn1<Date | string | number, Date>
+  const toDate: CurriedFn1<any, Date>
   namespace toDate {}
 
-  const toDateWithOptions: CurriedFn2<Options, Date | string | number, Date>
+  const toDateWithOptions: CurriedFn2<Options, any, Date>
   namespace toDateWithOptions {}
 }
 
@@ -8372,7 +8372,7 @@ declare module 'date-fns/esm' {
   namespace isTuesday {}
 
   function isValid (
-    date: Date | string | number,
+    date: any,
     options?: Options
   ): boolean
   namespace isValid {}
@@ -8674,7 +8674,7 @@ declare module 'date-fns/esm' {
   namespace subYears {}
 
   function toDate (
-    argument: Date | string | number,
+    argument: any,
     options?: Options
   ): Date
   namespace toDate {}
@@ -11215,10 +11215,10 @@ declare module 'date-fns/esm/fp' {
   const isTuesdayWithOptions: CurriedFn2<Options, Date | string | number, boolean>
   namespace isTuesdayWithOptions {}
 
-  const isValid: CurriedFn1<Date | string | number, boolean>
+  const isValid: CurriedFn1<any, boolean>
   namespace isValid {}
 
-  const isValidWithOptions: CurriedFn2<Options, Date | string | number, boolean>
+  const isValidWithOptions: CurriedFn2<Options, any, boolean>
   namespace isValidWithOptions {}
 
   const isWednesday: CurriedFn1<Date | string | number, boolean>
@@ -11491,10 +11491,10 @@ declare module 'date-fns/esm/fp' {
   const subYearsWithOptions: CurriedFn3<Options, number, Date | string | number, Date>
   namespace subYearsWithOptions {}
 
-  const toDate: CurriedFn1<Date | string | number, Date>
+  const toDate: CurriedFn1<any, Date>
   namespace toDate {}
 
-  const toDateWithOptions: CurriedFn2<Options, Date | string | number, Date>
+  const toDateWithOptions: CurriedFn2<Options, any, Date>
   namespace toDateWithOptions {}
 }
 
@@ -17239,7 +17239,7 @@ interface dateFns {
   ): boolean
 
   isValid(
-    date: Date | string | number,
+    date: any,
     options?: Options
   ): boolean
 
@@ -17495,7 +17495,7 @@ interface dateFns {
   ): Date
 
   toDate(
-    argument: Date | string | number,
+    argument: any,
     options?: Options
   ): Date
 }