diff --git a/lib/__tests__/is-disabled.js b/lib/__tests__/is-disabled.js
index 2b84cce8e..ed34f98cf 100644
--- a/lib/__tests__/is-disabled.js
+++ b/lib/__tests__/is-disabled.js
@@ -9,64 +9,130 @@ describe('assert.dom(...).isDisabled()', () => {
     assert = new TestAssertions();
   });
 
-  describe('input tags', () => {
-    test('succeeds when input is disabled', () => {
-      document.body.innerHTML = '<input disabled>';
+  test('with custom message', () => {
+    document.body.innerHTML = '<input type="text">';
+
+    assert.dom('input').isDisabled('custom message');
+
+    expect(assert.results).toEqual([{
+      actual: 'Element input is not disabled',
+      expected: 'Element input is disabled',
+      message: 'custom message',
+      result: false,
+    }]);
+  });
+
+  describe('with HTMLElement', () => {
+    let element;
+
+    beforeEach(() => {
+      document.body.innerHTML = '<input type="text" disabled>';
+      element = document.querySelector('input');
+    });
+
+    test('succeeds if element is disabled', () => {
+      assert.dom(element).isDisabled();
+
+      expect(assert.results).toEqual([{
+        actual: 'Element input[type="text"][disabled] is disabled',
+        expected: 'Element input[type="text"][disabled] is disabled',
+        message: 'Element input[type="text"][disabled] is disabled',
+        result: true,
+      }]);
+    });
+
+    test('fails if element is not disabled', () => {
+      element.disabled = false;
+      assert.dom(element).isDisabled();
+
+      expect(assert.results).toEqual([{
+        actual: 'Element input[type="text"] is not disabled',
+        expected: 'Element input[type="text"] is disabled',
+        message: 'Element input[type="text"] is disabled',
+        result: false,
+      }]);
+    });
+
+    test('fails for missing element', () => {
+      assert.dom(null).isDisabled();
+
+      expect(assert.results).toEqual([{
+        message: 'Element <unknown> exists',
+        result: false,
+      }]);
+    });
+
+    test('succeeds if element is disabled with text', () => {
+      document.body.innerHTML = '<input type="text" disabled="false">';
+      element = document.querySelector('input');
 
       assert.dom('input').isDisabled();
-      assert.dom(document.querySelector('input')).isDisabled();
 
       expect(assert.results).toEqual([{
         actual: 'Element input is disabled',
         expected: 'Element input is disabled',
         message: 'Element input is disabled',
         result: true,
-      }, {
-        actual: 'Element input[disabled] is disabled',
-        expected: 'Element input[disabled] is disabled',
-        message: 'Element input[disabled] is disabled',
-        result: true,
       }]);
     });
+  });
 
-    test('fails when input is not disabled', () => {
-      document.body.innerHTML = '<input>';
+  describe('with selector', () => {
+    beforeEach(() => {
+      document.body.innerHTML = '<input type="text" disabled>';
+    });
 
+    test('succeeds if element is disabled', () => {
       assert.dom('input').isDisabled();
-      assert.dom(document.querySelector('input')).isDisabled();
 
       expect(assert.results).toEqual([{
-        actual: 'Element input is not disabled',
+        actual: 'Element input is disabled',
         expected: 'Element input is disabled',
         message: 'Element input is disabled',
-        result: false,
-      }, {
+        result: true,
+      }]);
+    });
+
+    test('fails if element is not disabled', () => {
+      document.querySelector('input').disabled = false;
+      assert.dom('input').isDisabled();
+
+      expect(assert.results).toEqual([{
         actual: 'Element input is not disabled',
         expected: 'Element input is disabled',
         message: 'Element input is disabled',
         result: false,
       }]);
     });
-  });
-
-  describe('non-disablable elements', () => {
-    test('fails when element does not support disabled', () => {
-      document.body.innerHTML = '<div id="dis" disabled><div>';
 
-      assert.dom('div#dis').isDisabled();
-      assert.dom(document.querySelector('div#dis')).isDisabled();
+    test('fails for missing element', () => {
+      assert.dom('input[type="password"]').isDisabled();
 
       expect(assert.results).toEqual([{
-        actual: 'Element div#dis does not support disabled',
-        expected: 'Element div#dis is disabled',
-        message: 'Element div#dis is disabled',
-        result: false,
-      }, {
-        actual: 'Element div#dis[disabled] does not support disabled',
-        expected: 'Element div#dis[disabled] is disabled',
-        message: 'Element div#dis[disabled] is disabled',
+        message: 'Element input[type="password"] exists',
         result: false,
       }]);
     });
+
+    test('succeeds if element is disabled with text', () => {
+      document.body.innerHTML = '<input type="text" disabled="false">';
+      assert.dom('input').isDisabled();
+
+      expect(assert.results).toEqual([{
+        actual: 'Element input is disabled',
+        expected: 'Element input is disabled',
+        message: 'Element input is disabled',
+        result: true,
+      }]);
+    });
+  });
+
+  test('throws for unexpected parameter types', () => {
+    expect(() => assert.dom(5).isDisabled()).toThrow('Unexpected Parameter: 5');
+    expect(() => assert.dom(true).isDisabled()).toThrow('Unexpected Parameter: true');
+    expect(() => assert.dom(undefined).isDisabled()).toThrow('Unexpected Parameter: undefined');
+    expect(() => assert.dom({}).isDisabled()).toThrow('Unexpected Parameter: [object Object]');
+    expect(() => assert.dom(document).isDisabled()).toThrow('Unexpected Parameter: [object HTMLDocument]');
+    expect(() => assert.dom(document.createElement('div')).isDisabled()).toThrow('Unexpected Element Type: [object HTMLDivElement]');
   });
 });
diff --git a/lib/assertions.js b/lib/assertions.js
index 6aea0807f..7f02a2d01 100644
--- a/lib/assertions.js
+++ b/lib/assertions.js
@@ -7,7 +7,7 @@ import isRequired from './assertions/is-required';
 import isNotRequired from './assertions/is-not-required';
 import isVisible from './assertions/is-visible';
 import isNotVisible from './assertions/is-not-visible';
-import isNotDisabled from './assertions/is-not-disabled';
+import isDisabled from './assertions/is-disabled';
 
 import elementToString from './helpers/element-to-string';
 import collapseWhitespace from './helpers/collapse-whitespace';
@@ -318,24 +318,7 @@ export default class DOMAssertions {
    * @see {@link #isNotDisabled}
    */
   isDisabled(message) {
-    let element = this.findTargetElement();
-
-    let expected = `Element ${this.targetDescription} is disabled`;
-    let actual = `Element ${this.targetDescription} is disabled`;
-    let result = element.disabled;
-
-    if (result === false) {
-      actual = `Element ${this.targetDescription} is not disabled`;
-    } else if(result === undefined) {
-      actual = `Element ${this.targetDescription} does not support disabled`;
-      result = false;
-    }
-
-    if (!message) {
-      message = expected;
-    }
-
-    this.pushResult({ result, actual, expected, message });
+    isDisabled.call(this, message);
   }
 
   /**
@@ -351,7 +334,7 @@ export default class DOMAssertions {
    * @see {@link #isDisabled}
    */
   isNotDisabled(message) {
-    isNotDisabled.call(this, message);
+    isDisabled.call(this, message, { inverted: true });
   }
 
   /**
diff --git a/lib/assertions/is-disabled.js b/lib/assertions/is-disabled.js
new file mode 100644
index 000000000..7bccfc715
--- /dev/null
+++ b/lib/assertions/is-disabled.js
@@ -0,0 +1,34 @@
+export default function isDisabled(message, options = {}) {
+  let { inverted } = options;
+
+  let element = this.findTargetElement();
+  if (!element) return;
+
+  if (!(
+      element instanceof HTMLInputElement ||
+      element instanceof HTMLTextAreaElement ||
+      element instanceof HTMLSelectElement ||
+      element instanceof HTMLButtonElement ||
+      element instanceof HTMLOptGroupElement ||
+      element instanceof HTMLOptionElement ||
+      element instanceof HTMLFieldSetElement
+    )) {
+    throw new TypeError(`Unexpected Element Type: ${element.toString()}`);
+  }
+
+  let result = element.disabled === !inverted;
+
+  let actual = element.disabled === false
+    ? `Element ${this.targetDescription} is not disabled`
+    : `Element ${this.targetDescription} is disabled`;
+
+  let expected = inverted
+    ? `Element ${this.targetDescription} is not disabled`
+    : `Element ${this.targetDescription} is disabled`;
+
+  if (!message) {
+    message = expected;
+  }
+
+  this.pushResult({ result, actual, expected, message });
+}
diff --git a/lib/assertions/is-not-disabled.js b/lib/assertions/is-not-disabled.js
deleted file mode 100644
index 6e557fc0f..000000000
--- a/lib/assertions/is-not-disabled.js
+++ /dev/null
@@ -1,26 +0,0 @@
-export default function notDisabled(message) {
-  let element = this.findTargetElement();
-  if (!element) return;
-
-  if (!(
-    element instanceof HTMLInputElement ||
-    element instanceof HTMLTextAreaElement ||
-    element instanceof HTMLSelectElement ||
-    element instanceof HTMLButtonElement ||
-    element instanceof HTMLOptGroupElement ||
-    element instanceof HTMLOptionElement ||
-    element instanceof HTMLFieldSetElement
-  )) {
-    throw new TypeError(`Unexpected Element Type: ${element.toString()}`);
-  }
-
-  let result = element.disabled === false;
-  let actual = result ? `Element ${this.targetDescription} is not disabled` : `Element ${this.targetDescription} is disabled`;
-  let expected = `Element ${this.targetDescription} is not disabled`;
-
-  if (!message) {
-    message = expected;
-  }
-
-  this.pushResult({ result, actual, expected, message });
-}