diff --git a/src/renderers/dom/fiber/ReactDOMFiberComponent.js b/src/renderers/dom/fiber/ReactDOMFiberComponent.js
index 9b46875c92c8e..5df978dde49ef 100644
--- a/src/renderers/dom/fiber/ReactDOMFiberComponent.js
+++ b/src/renderers/dom/fiber/ReactDOMFiberComponent.js
@@ -922,8 +922,7 @@ var ReactDOMFiberComponent = {
       var extraAttributeNames: Set<string> = new Set();
       var attributes = domElement.attributes;
       for (var i = 0; i < attributes.length; i++) {
-        // TODO: Do we need to lower case this to get case insensitive matches?
-        var name = attributes[i].name;
+        var name = attributes[i].name.toLowerCase();
         switch (name) {
           // Built-in attributes are whitelisted
           // TODO: Once these are gone from the server renderer, we don't need
diff --git a/src/renderers/dom/shared/DOMProperty.js b/src/renderers/dom/shared/DOMProperty.js
index a3641c932dfdd..1edc7261d1fd0 100644
--- a/src/renderers/dom/shared/DOMProperty.js
+++ b/src/renderers/dom/shared/DOMProperty.js
@@ -119,7 +119,11 @@ var DOMPropertyInjection = {
       if (DOMAttributeNames.hasOwnProperty(propName)) {
         var attributeName = DOMAttributeNames[propName];
 
-        DOMProperty.aliases[attributeName] = true;
+        DOMProperty.aliases[attributeName.toLowerCase()] = true;
+
+        if (lowerCased !== attributeName) {
+          DOMProperty.aliases[lowerCased] = true;
+        }
 
         propertyInfo.attributeName = attributeName;
         if (__DEV__) {
@@ -238,10 +242,6 @@ var DOMProperty = {
       return true;
     }
 
-    if (name.toLowerCase() !== name) {
-      return false;
-    }
-
     switch (typeof value) {
       case 'undefined':
       case 'boolean':
diff --git a/src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js b/src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js
index 74a9f1eef50bc..9cdb405109944 100644
--- a/src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js
+++ b/src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js
@@ -1992,30 +1992,14 @@ describe('ReactDOMComponent', () => {
       expect(el.getAttribute('ajaxify')).toBe('ajaxy');
     });
 
-    it('only allows lower-case data attributes', function() {
-      spyOn(console, 'error');
-
+    it('allows cased data attributes', function() {
       var el = ReactTestUtils.renderIntoDocument(<div data-fooBar="true" />);
-
-      expect(el.hasAttribute('data-foobar')).toBe(false);
-
-      expectDev(console.error.calls.argsFor(0)[0]).toContain(
-        'Warning: Invalid DOM property `data-fooBar`. Custom attributes ' +
-          'and data attributes must be lower case. Instead use `data-foobar`',
-      );
+      expect(el.getAttribute('data-foobar')).toBe('true');
     });
 
-    it('only allows lower-case custom attributes', function() {
-      spyOn(console, 'error');
-
+    it('allows cased custom attributes', function() {
       var el = ReactTestUtils.renderIntoDocument(<div fooBar="true" />);
-
-      expect(el.hasAttribute('foobar')).toBe(false);
-
-      expectDev(console.error.calls.argsFor(0)[0]).toContain(
-        'Warning: Invalid DOM property `fooBar`. Custom attributes ' +
-          'and data attributes must be lower case. Instead use `foobar`',
-      );
+      expect(el.getAttribute('foobar')).toBe('true');
     });
   });
 });
diff --git a/src/renderers/dom/shared/__tests__/ReactDOMServerIntegration-test.js b/src/renderers/dom/shared/__tests__/ReactDOMServerIntegration-test.js
index 8080371bb3605..8c7af5c04fe9e 100644
--- a/src/renderers/dom/shared/__tests__/ReactDOMServerIntegration-test.js
+++ b/src/renderers/dom/shared/__tests__/ReactDOMServerIntegration-test.js
@@ -615,6 +615,12 @@ describe('ReactDOMServerIntegration', () => {
         expect(e.hasAttribute('className')).toBe(false);
       });
 
+      itRenders('no classname prop', async render => {
+        const e = await render(<div classname="test" />, 1);
+        expect(e.hasAttribute('class')).toBe(false);
+        expect(e.hasAttribute('classname')).toBe(false);
+      });
+
       itRenders('no className prop when given the alias', async render => {
         const e = await render(<div class="test" />, 1);
         expect(e.className).toBe('');
@@ -793,9 +799,32 @@ describe('ReactDOMServerIntegration', () => {
       });
     });
 
+    describe('cased attributes', function() {
+      itRenders('no badly cased aliased HTML attribute', async render => {
+        const e = await render(<meta httpequiv="refresh" />, 1);
+        expect(e.hasAttribute('http-equiv')).toBe(false);
+        expect(e.hasAttribute('httpequiv')).toBe(false);
+      });
+
+      itRenders('no badly cased SVG attribute', async render => {
+        const e = await render(<text textlength="10" />, 1);
+        expect(e.hasAttribute('textLength')).toBe(false);
+      });
+
+      itRenders('no badly cased aliased SVG attribute', async render => {
+        const e = await render(<text strokedasharray="10 10" />, 1);
+        expect(e.hasAttribute('strokedasharray')).toBe(false);
+      });
+
+      itRenders('no badly cased original SVG attribute that is aliased', async render => {
+        const e = await render(<text stroke-dasharray="10 10" />, 1);
+        expect(e.hasAttribute('stroke-dasharray')).toBe(false);
+      });
+    });
+
     describe('unknown attributes', function() {
       itRenders('unknown attributes', async render => {
-        const e = await render(<div foo="bar" />, 0);
+        const e = await render(<div foo="bar" />);
         expect(e.getAttribute('foo')).toBe('bar');
       });
 
@@ -809,13 +838,21 @@ describe('ReactDOMServerIntegration', () => {
         expect(e.hasAttribute('data-foo')).toBe(false);
       });
 
-      itRenders('no unknown data- attributes with casing', async render => {
-        const e = await render(<div data-fooBar={null} />, 1);
-        expect(e.hasAttribute('data-foobar')).toBe(false);
+      itRenders('unknown data- attributes with casing', async render => {
+        const e = await render(<div data-fooBar="true" />);
+        expect(e.getAttribute('data-fooBar')).toBe('true');
       });
 
+      itRenders(
+        'no unknown data- attributes with casing and null value',
+        async render => {
+          const e = await render(<div data-fooBar={null} />);
+          expect(e.hasAttribute('data-fooBar')).toBe(false);
+        },
+      );
+
       itRenders('custom attributes for non-standard elements', async render => {
-        const e = await render(<nonstandard foo="bar" />, 0);
+        const e = await render(<nonstandard foo="bar" />);
         expect(e.getAttribute('foo')).toBe('bar');
       });
 
@@ -848,9 +885,9 @@ describe('ReactDOMServerIntegration', () => {
         },
       );
 
-      itRenders('no cased custom attributes', async render => {
-        const e = await render(<div fooBar="test" />, 1);
-        expect(e.hasAttribute('fooBar')).toBe(false);
+      itRenders('cased custom attributes', async render => {
+        const e = await render(<div fooBar="test" />);
+        expect(e.getAttribute('fooBar')).toBe('test');
       });
     });
 
diff --git a/src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js b/src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js
index f71af11a2e80c..11da5af3c315d 100644
--- a/src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js
+++ b/src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js
@@ -101,20 +101,6 @@ if (__DEV__) {
       return true;
     }
 
-    // Otherwise, we have a custom attribute. Custom attributes should always
-    // be lowercase.
-    if (lowerCasedName !== name) {
-      warning(
-        false,
-        'Invalid DOM property `%s`. Custom attributes and data attributes ' +
-          'must be lower case. Instead use `%s`.%s',
-        name,
-        lowerCasedName,
-        getStackAddendum(debugID),
-      );
-      return true;
-    }
-
     return DOMProperty.shouldSetAttribute(name, value);
   };
 }