diff --git a/README.md b/README.md
index 0e8e9ca..46a8704 100644
--- a/README.md
+++ b/README.md
@@ -35,6 +35,17 @@ var count = normalize('number', function(a, b) {
 }, 1, 2);
 // count === 3
 
+// Values one of multiple types are returned
+var isEnabled = normalize(['string', 'boolean'], true);
+// isEnabled === true
+
+// Values matching predicate are returned
+var now = new Date();
+var enabledSince = normalize(function(value) {
+  return value.constructor === Date;
+}, now);
+// enabledSince === now
+
 // Convenience methods are available
 var result = normalize.object({});
 var result = normalize.number(1);
@@ -47,15 +58,19 @@ var result = normalize.undefined(undefined);
 
 ## API
 
-### `normalize(type, value[, ...appliedArguments])`
+### `normalize(predicate, value[, ...appliedArguments])`
+
+Takes a predicate function `predicate` to test against `value`. Also optionally takes any extra arguments to apply to `value` if `value` is a function.
+
+If the result of `predicate(value)` is true, the value is returned. If false and `value` is a function, the function is called with any extra arguments supplied to `normalize`.
 
-Takes a string of the `type` to match and a `value` to compare with `typeof`. Also optionally takes any extra arguments to apply to `value` if `value` is a function.
+If `value` is neither match for the predicate or a function, `null` is returned.
 
-If the results of `typeof value === type` is true, the value is returned. If false and `value` is a function, the function is called with any extra arguments supplied to `normalize`.
+If `value` is a function and the result of calling the function does not match the predicate, `null` is returned.
 
-If `value` is neither a type match or a function, `null` is returned.
+If `predicate` is a string, the applied predicate is `typeof value === predicate`.
 
-If `value` is a function and the result of calling the function does not match the type, `null` is returned.
+If `predicate` is an array, `normalized` is called with each element in turn until one matches or none matches.
 
 #### `normalize.object(value[, ...appliedArguments])`
 
diff --git a/index.js b/index.js
index a68ed95..3561d97 100644
--- a/index.js
+++ b/index.js
@@ -13,7 +13,7 @@ var types = [
 function normalize(type, value) {
   var args = Array.prototype.slice.call(arguments, 2);
 
-  var isType = typeof value === type;
+  var isType = conforms(type, value);
   var isFunction = typeof value === 'function';
 
   if (!isType && !isFunction) {
@@ -33,6 +33,18 @@ function normalize(type, value) {
   return result;
 }
 
+function conforms(type, value) {
+  if (typeof type === 'string') {
+    return typeof value === type;
+  }
+  if (typeof type === 'function') {
+    return !!type(value);
+  }
+  return type.some(function(type) {
+    return conforms(type, value);
+  });
+}
+
 // Add methods for each type
 types.forEach(function(type) {
   normalize[type] = normalize.bind(null, type);
diff --git a/package.json b/package.json
index 93cbfc3..83755a2 100644
--- a/package.json
+++ b/package.json
@@ -17,7 +17,7 @@
     "lint": "eslint . && jscs index.js test/",
     "pretest": "npm run lint",
     "test": "mocha --async-only",
-    "cover": "istanbul cover _mocha --report lcovonly",
+    "cover": "istanbul cover node_modules/mocha/bin/_mocha --report lcovonly",
     "coveralls": "npm run cover && istanbul-coveralls"
   },
   "dependencies": {},
diff --git a/test/index.js b/test/index.js
index 73f8e36..c695756 100644
--- a/test/index.js
+++ b/test/index.js
@@ -22,6 +22,53 @@ describe('normalize', function() {
     done();
   });
 
+  it('supports arrays for the type parameter', function(done) {
+    var type = ['string'];
+    var value = 'test string';
+    var result = normalize(type, value);
+    expect(result).toEqual(value);
+    done();
+  });
+
+  it('compares each type and the type of the value', function(done) {
+    var type = ['number', 'string', 'object'];
+    var value = 'test string';
+    var result = normalize(type, value);
+    expect(result).toEqual(value);
+    done();
+  });
+
+  it('returns null if value does not match any type', function(done) {
+    var type = ['string', 'undefined'];
+    var value = 1;
+    var result = normalize(type, value);
+    expect(result).toEqual(null);
+    done();
+  });
+
+  it('supports functions for the type parameter', function(done) {
+    var type = function() {
+      return true;
+    };
+    var value = 1;
+    var result = normalize(type, value);
+    expect(result).toEqual(value);
+    done();
+  });
+
+  it('calls the type function to check validity', function(done) {
+    var called = false;
+    var type = function() {
+      called = true;
+      return false;
+    };
+    var value = 1;
+    var result = normalize(type, value);
+    expect(result).toEqual(null);
+    expect(called).toEqual(true);
+    done();
+  });
+
   it('calls the value if it is a function', function(done) {
     var type = 'string';
     var expected = 'test string';