diff --git a/dist/core/rules/attr-no-duplication.js b/dist/core/rules/attr-no-duplication.js
index 35912a1d5..97109025b 100644
--- a/dist/core/rules/attr-no-duplication.js
+++ b/dist/core/rules/attr-no-duplication.js
@@ -12,7 +12,7 @@ exports.default = {
             const mapAttrName = {};
             for (let i = 0, l = attrs.length; i < l; i++) {
                 attr = attrs[i];
-                attrName = attr.name;
+                attrName = attr.name.toLowerCase();
                 if (mapAttrName[attrName] === true) {
                     reporter.error(`Duplicate of attribute name [ ${attr.name} ] was found.`, event.line, col + attr.index, this, attr.raw);
                 }
@@ -21,4 +21,4 @@ exports.default = {
         });
     },
 };
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\ No newline at end of file
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\ No newline at end of file
diff --git a/dist/core/rules/src-not-empty.js b/dist/core/rules/src-not-empty.js
index 0db9c23d9..4bc01a884 100644
--- a/dist/core/rules/src-not-empty.js
+++ b/dist/core/rules/src-not-empty.js
@@ -5,16 +5,17 @@ exports.default = {
     description: 'The src attribute of an img(script,link) must have a value.',
     init(parser, reporter) {
         parser.addListener('tagstart', (event) => {
-            const tagName = event.tagName;
+            const tagName = event.tagName.toLowerCase();
             const attrs = event.attrs;
             let attr;
             const col = event.col + tagName.length + 1;
             for (let i = 0, l = attrs.length; i < l; i++) {
                 attr = attrs[i];
+                const attrName = attr.name.toLowerCase();
                 if (((/^(img|script|embed|bgsound|iframe)$/.test(tagName) === true &&
-                    attr.name === 'src') ||
-                    (tagName === 'link' && attr.name === 'href') ||
-                    (tagName === 'object' && attr.name === 'data')) &&
+                    attrName === 'src') ||
+                    (tagName === 'link' && attrName === 'href') ||
+                    (tagName === 'object' && attrName === 'data')) &&
                     attr.value === '') {
                     reporter.error(`The attribute [ ${attr.name} ] of the tag [ ${tagName} ] must have a value.`, event.line, col + attr.index, this, attr.raw);
                 }
@@ -22,4 +23,4 @@ exports.default = {
         });
     },
 };
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\ No newline at end of file
+//# sourceMappingURL=data:application/json;base64,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
\ No newline at end of file
diff --git a/src/core/rules/attr-no-duplication.ts b/src/core/rules/attr-no-duplication.ts
index f7b4e4d9c..fada923d9 100644
--- a/src/core/rules/attr-no-duplication.ts
+++ b/src/core/rules/attr-no-duplication.ts
@@ -14,7 +14,9 @@ export default {
 
       for (let i = 0, l = attrs.length; i < l; i++) {
         attr = attrs[i]
-        attrName = attr.name
+        // HTML attribute names are ASCII case insensitive, so id and ID on the
+        // same element are a duplicate.
+        attrName = attr.name.toLowerCase()
 
         if (mapAttrName[attrName] === true) {
           reporter.error(
diff --git a/src/core/rules/src-not-empty.ts b/src/core/rules/src-not-empty.ts
index 4510e151d..1a9dd27ae 100644
--- a/src/core/rules/src-not-empty.ts
+++ b/src/core/rules/src-not-empty.ts
@@ -5,19 +5,23 @@ export default {
   description: 'The src attribute of an img(script,link) must have a value.',
   init(parser, reporter) {
     parser.addListener('tagstart', (event) => {
-      const tagName = event.tagName
+      // HTML tag and attribute names are ASCII case insensitive, so compare
+      // against the lowercased form. The parser hands them over exactly as they
+      // were written.
+      const tagName = event.tagName.toLowerCase()
       const attrs = event.attrs
       let attr
       const col = event.col + tagName.length + 1
 
       for (let i = 0, l = attrs.length; i < l; i++) {
         attr = attrs[i]
+        const attrName = attr.name.toLowerCase()
 
         if (
           ((/^(img|script|embed|bgsound|iframe)$/.test(tagName) === true &&
-            attr.name === 'src') ||
-            (tagName === 'link' && attr.name === 'href') ||
-            (tagName === 'object' && attr.name === 'data')) &&
+            attrName === 'src') ||
+            (tagName === 'link' && attrName === 'href') ||
+            (tagName === 'object' && attrName === 'data')) &&
           attr.value === ''
         ) {
           reporter.error(
diff --git a/test/rules/attr-no-duplication.spec.js b/test/rules/attr-no-duplication.spec.js
index 498ae2ef4..851eff5e5 100644
--- a/test/rules/attr-no-duplication.spec.js
+++ b/test/rules/attr-no-duplication.spec.js
@@ -15,6 +15,15 @@ describe(`Rules: ${ruleId}`, () => {
     expect(messages[0].col).toBe(12)
   })
 
+  it('Attribute name duplicated in a different case should result in an error', () => {
+    // HTML attribute names are ASCII case insensitive, so href and HREF on the
+    // same element are the same attribute.
+    const code = '<a href="a" HREF="b">bbb</a>'
+    const messages = HTMLHint.verify(code, ruleOptions)
+    expect(messages.length).toBe(1)
+    expect(messages[0].rule.id).toBe(ruleId)
+  })
+
   it('Attribute name not been duplication should not result in an error', () => {
     const code = '<a href="a">bbb</a>'
     const messages = HTMLHint.verify(code, ruleOptions)
diff --git a/test/rules/src-not-empty.spec.js b/test/rules/src-not-empty.spec.js
index 1005b7c9b..a22faa719 100644
--- a/test/rules/src-not-empty.spec.js
+++ b/test/rules/src-not-empty.spec.js
@@ -20,6 +20,20 @@ describe(`Rules: ${ruleId}`, () => {
     expect(messages.length).toBe(0)
   })
 
+  it('Src be empty should result in an error whatever the case', () => {
+    // HTML tag and attribute names are ASCII case insensitive, so these are four
+    // spellings of one bug and all four have to be reported.
+    const code = '<img src="" /><img SRC="" /><IMG src="" /><IMG SRC="" />'
+    const messages = HTMLHint.verify(code, ruleOptions)
+    expect(messages.length).toBe(4)
+  })
+
+  it('Uppercase href and data should result in an error', () => {
+    const code = '<LINK HREF="" type="text/css" /><OBJECT DATA="">'
+    const messages = HTMLHint.verify(code, ruleOptions)
+    expect(messages.length).toBe(2)
+  })
+
   it('Src be not set value should not result in an error', () => {
     const code =
       '<img width="200" /><script></script><link type="text/css" /><embed width="200"><bgsound /><iframe width="200"><object width="200">'