diff --git a/demo/markdownlint-browser.js b/demo/markdownlint-browser.js
index 24e8b625a..a98df79cb 100644
--- a/demo/markdownlint-browser.js
+++ b/demo/markdownlint-browser.js
@@ -168,6 +168,16 @@ function cloneIfUrl(url) {
 }
 module.exports.cloneIfUrl = cloneIfUrl;
 
+/**
+ * Gets a Regular Expression for matching the specified HTML attribute.
+ *
+ * @param {string} name HTML attribute name.
+ * @returns {RegExp} Regular Expression for matching.
+ */
+module.exports.getHtmlAttributeRe = function getHtmlAttributeRe(name) {
+  return new RegExp("\\s".concat(name, "\\s*=\\s*['\"]?([^'\"\\s>]*)"), "iu");
+};
+
 /**
  * Returns true iff the input line is blank (contains nothing, whitespace, or
  * comments (unclosed start/end comments allowed)).
@@ -5992,13 +6002,12 @@ function _unsupportedIterableToArray(o, minLen) { if (!o) return; if (typeof o =
 function _arrayLikeToArray(arr, len) { if (len == null || len > arr.length) len = arr.length; for (var i = 0, arr2 = new Array(len); i < len; i++) arr2[i] = arr[i]; return arr2; }
 var _require = __webpack_require__(/*! ../helpers */ "../helpers/helpers.js"),
   addError = _require.addError,
+  getHtmlAttributeRe = _require.getHtmlAttributeRe,
   nextLinesRe = _require.nextLinesRe;
 var _require2 = __webpack_require__(/*! ../helpers/micromark.cjs */ "../helpers/micromark.cjs"),
   filterByTypes = _require2.filterByTypes,
   getHtmlTagInfo = _require2.getHtmlTagInfo;
-
-// Regular expression for identifying alt attribute
-var altRe = /\salt=/i;
+var altRe = getHtmlAttributeRe("alt");
 module.exports = {
   "names": ["MD045", "no-alt-text"],
   "description": "Images should have alternate text (alt text)",
@@ -6038,7 +6047,7 @@ module.exports = {
           startLine = htmlText.startLine,
           text = htmlText.text;
         var htmlTagInfo = getHtmlTagInfo(htmlText);
-        if (htmlTagInfo && htmlTagInfo.name.toLowerCase() === "img" && !altRe.test(text)) {
+        if (htmlTagInfo && !htmlTagInfo.close && htmlTagInfo.name.toLowerCase() === "img" && !altRe.test(text)) {
           var _range = [startColumn, text.replace(nextLinesRe, "").length];
           addError(onError, startLine, undefined, undefined, _range);
         }
@@ -6292,15 +6301,16 @@ function _unsupportedIterableToArray(o, minLen) { if (!o) return; if (typeof o =
 function _arrayLikeToArray(arr, len) { if (len == null || len > arr.length) len = arr.length; for (var i = 0, arr2 = new Array(len); i < len; i++) arr2[i] = arr[i]; return arr2; }
 var _require = __webpack_require__(/*! ../helpers */ "../helpers/helpers.js"),
   addError = _require.addError,
-  addErrorDetailIf = _require.addErrorDetailIf;
+  addErrorDetailIf = _require.addErrorDetailIf,
+  getHtmlAttributeRe = _require.getHtmlAttributeRe;
 var _require2 = __webpack_require__(/*! ../helpers/micromark.cjs */ "../helpers/micromark.cjs"),
   filterByPredicate = _require2.filterByPredicate,
   filterByTypes = _require2.filterByTypes,
   getHtmlTagInfo = _require2.getHtmlTagInfo;
 
 // Regular expression for identifying HTML anchor names
-var idRe = /[\t-\r \xA0\u1680\u2000-\u200A\u2028\u2029\u202F\u205F\u3000\uFEFF]id[\t-\r \xA0\u1680\u2000-\u200A\u2028\u2029\u202F\u205F\u3000\uFEFF]*=[\t-\r \xA0\u1680\u2000-\u200A\u2028\u2029\u202F\u205F\u3000\uFEFF]*["']?((?:(?![\t-\r "'>\xA0\u1680\u2000-\u200A\u2028\u2029\u202F\u205F\u3000\uD800-\uDFFF\uFEFF])[\s\S]|[\uD800-\uDBFF][\uDC00-\uDFFF])+)/i;
-var nameRe = /[\t-\r \xA0\u1680\u2000-\u200A\u2028\u2029\u202F\u205F\u3000\uFEFF]name[\t-\r \xA0\u1680\u2000-\u200A\u2028\u2029\u202F\u205F\u3000\uFEFF]*=[\t-\r \xA0\u1680\u2000-\u200A\u2028\u2029\u202F\u205F\u3000\uFEFF]*["']?((?:(?![\t-\r "'>\xA0\u1680\u2000-\u200A\u2028\u2029\u202F\u205F\u3000\uD800-\uDFFF\uFEFF])[\s\S]|[\uD800-\uDBFF][\uDC00-\uDFFF])+)/i;
+var idRe = getHtmlAttributeRe("id");
+var nameRe = getHtmlAttributeRe("name");
 var anchorRe = /\{(#[0-9a-z]+(?:[\x2D_][0-9a-z]+)*)\}/g;
 
 // Sets for filtering heading tokens during conversion
@@ -6393,7 +6403,7 @@ module.exports = {
         var htmlTagInfo = getHtmlTagInfo(token);
         if (htmlTagInfo && !htmlTagInfo.close) {
           var anchorMatch = idRe.exec(token.text) || htmlTagInfo.name.toLowerCase() === "a" && nameRe.exec(token.text);
-          if (anchorMatch) {
+          if (anchorMatch && anchorMatch.length > 0) {
             fragments.set("#".concat(anchorMatch[1]), 0);
           }
         }
diff --git a/helpers/helpers.js b/helpers/helpers.js
index 2ef5a2974..59230fe3c 100644
--- a/helpers/helpers.js
+++ b/helpers/helpers.js
@@ -126,6 +126,16 @@ function cloneIfUrl(url) {
 }
 module.exports.cloneIfUrl = cloneIfUrl;
 
+/**
+ * Gets a Regular Expression for matching the specified HTML attribute.
+ *
+ * @param {string} name HTML attribute name.
+ * @returns {RegExp} Regular Expression for matching.
+ */
+module.exports.getHtmlAttributeRe = function getHtmlAttributeRe(name) {
+  return new RegExp(`\\s${name}\\s*=\\s*['"]?([^'"\\s>]*)`, "iu");
+};
+
 /**
  * Returns true iff the input line is blank (contains nothing, whitespace, or
  * comments (unclosed start/end comments allowed)).
diff --git a/lib/md045.js b/lib/md045.js
index e5ab4a7ed..d2b0a3846 100644
--- a/lib/md045.js
+++ b/lib/md045.js
@@ -2,11 +2,10 @@
 
 "use strict";
 
-const { addError, nextLinesRe } = require("../helpers");
+const { addError, getHtmlAttributeRe, nextLinesRe } = require("../helpers");
 const { filterByTypes, getHtmlTagInfo } = require("../helpers/micromark.cjs");
 
-// Regular expression for identifying alt attribute
-const altRe = /\salt=/i;
+const altRe = getHtmlAttributeRe("alt");
 
 module.exports = {
   "names": [ "MD045", "no-alt-text" ],
@@ -40,6 +39,7 @@ module.exports = {
       const htmlTagInfo = getHtmlTagInfo(htmlText);
       if (
         htmlTagInfo &&
+        !htmlTagInfo.close &&
         (htmlTagInfo.name.toLowerCase() === "img") &&
         !altRe.test(text)
       ) {
diff --git a/lib/md051.js b/lib/md051.js
index 98606bdad..bc0ff99a9 100644
--- a/lib/md051.js
+++ b/lib/md051.js
@@ -2,13 +2,14 @@
 
 "use strict";
 
-const { addError, addErrorDetailIf } = require("../helpers");
+const { addError, addErrorDetailIf, getHtmlAttributeRe } =
+  require("../helpers");
 const { filterByPredicate, filterByTypes, getHtmlTagInfo } =
   require("../helpers/micromark.cjs");
 
 // Regular expression for identifying HTML anchor names
-const idRe = /\sid\s*=\s*['"]?([^'"\s>]+)/iu;
-const nameRe = /\sname\s*=\s*['"]?([^'"\s>]+)/iu;
+const idRe = getHtmlAttributeRe("id");
+const nameRe = getHtmlAttributeRe("name");
 const anchorRe = /\{(#[a-z\d]+(?:[-_][a-z\d]+)*)\}/gu;
 
 // Sets for filtering heading tokens during conversion
@@ -101,7 +102,7 @@ module.exports = {
       if (htmlTagInfo && !htmlTagInfo.close) {
         const anchorMatch = idRe.exec(token.text) ||
           (htmlTagInfo.name.toLowerCase() === "a" && nameRe.exec(token.text));
-        if (anchorMatch) {
+        if (anchorMatch && anchorMatch.length > 0) {
           fragments.set(`#${anchorMatch[1]}`, 0);
         }
       }