diff --git a/packages/convict/README.md b/packages/convict/README.md
index a1a6c682..99bfa54e 100644
--- a/packages/convict/README.md
+++ b/packages/convict/README.md
@@ -78,6 +78,12 @@ var config = convict({
       format: String,
       default: 'users'
     }
+  },
+  admins: {
+    doc: 'Users with write access, or null to grant full access without login.',
+    format: Array,
+    nullable: true,
+    default: null
   }
 });
 
@@ -161,6 +167,7 @@ convict's goal of being more robust and collaborator friendly.
 * **Command-line arguments**: If the command-line argument specified by `arg` is supplied, it will overwrite the setting's default value or the value derived from `env`.
 * **Documentation**: The `doc` property is pretty self-explanatory. The nice part about having it in the schema rather than as a comment is that we can call `config.getSchemaString()` and have it displayed in the output.
 * **Sensitive values and secrets**: If `sensitive` is set to `true`, this value will be masked to `"[Sensitive]"` when `config.toString()` is called. This helps avoid disclosing secret keys when printing configuration at application start for debugging purposes.
+* **Null values**: If `nullable` is set to `true`, the value counts as valid not only if it matches the specified `format`, but also when it is `null`.
 
 
 ### Validation
@@ -180,6 +187,8 @@ You can find other format [here](https://www.npmjs.com/search?q=keywords:convict
 
 If `format` is set to one of the built-in JavaScript constructors, `Object`, `Array`, `String`, `Number`, `RegExp`, or `Boolean`, validation will use Object.prototype.toString.call to check that the setting is the proper type.
 
+If `nullable` is set to true, `null` will be a valid value as well.
+
 #### Custom format checking
 
 You can specify a custom format checking method on a property basis.
diff --git a/packages/convict/src/main.js b/packages/convict/src/main.js
index 9ee31fe9..e3a6a429 100644
--- a/packages/convict/src/main.js
+++ b/packages/convict/src/main.js
@@ -294,6 +294,11 @@ function normalizeSchema(name, node, props, fullName, env, argv, sensitive) {
   }
 
   o._format = function(x) {
+    // accept null if allowed before calling any format function
+    if (this.nullable && x === null) {
+      return
+    }
+
     try {
       newFormat(x, this)
     } catch (e) {
@@ -563,7 +568,7 @@ const convict = function convict(def, opts) {
       const parentKey = path.join('.')
       if (!(parentKey == '__proto__' || parentKey == 'constructor' || parentKey == 'prototype')) {
         const parent = walk(this._instance, parentKey, true)
-        parent[childKey] = v 
+        parent[childKey] = v
       }
       return this
     },
diff --git a/packages/convict/test/cases/nullable.js b/packages/convict/test/cases/nullable.js
new file mode 100644
index 00000000..6180d880
--- /dev/null
+++ b/packages/convict/test/cases/nullable.js
@@ -0,0 +1,14 @@
+'use strict'
+
+exports.conf = {
+  foo: {
+    default: null,
+    format: ['hello', 'world'],
+    nullable: true,
+  },
+  bar: {
+    default: null,
+    format: String,
+    nullable: true,
+  }
+}
diff --git a/packages/convict/test/cases/nullable.out b/packages/convict/test/cases/nullable.out
new file mode 100644
index 00000000..9e4336d1
--- /dev/null
+++ b/packages/convict/test/cases/nullable.out
@@ -0,0 +1,4 @@
+{
+  "foo": null,
+  "bar": null
+}