diff --git a/src/codemirror/6502.js b/src/codemirror/6502.js
deleted file mode 100644
index a7212fe5..00000000
--- a/src/codemirror/6502.js
+++ /dev/null
@@ -1,95 +0,0 @@
-// CodeMirror, copyright (c) by Marijn Haverbeke and others
-// Distributed under an MIT license: http://codemirror.net/LICENSE
-
-(function(mod) {
-  if (typeof exports == "object" && typeof module == "object") // CommonJS
-  mod(require("../../lib/codemirror"));
-  else if (typeof define == "function" && define.amd) // AMD
-  define(["../../lib/codemirror"], mod);
-  else // Plain browser env
-  mod(CodeMirror);
-})(function(CodeMirror) {
-"use strict";
-
-// 6502 DASM syntax
-
-CodeMirror.defineMode('6502', function(_config, parserConfig) {
-  var keywords1, keywords2;
-
-  var directives_list = [
-    'processor',
-    'byte','word','long',
-    'include','seg','dc','ds','dv','hex','err','org','rorg','echo','rend',
-    'align','subroutine','equ','eqm','set','mac','endm','mexit','ifconst',
-    'ifnconst','if','else','endif','eif','repeat','repend'];
-  var directives = new Map();
-  directives_list.forEach(function(s) { directives.set(s, 'keyword'); });
-
-  var opcodes = /^[a-z][a-z][a-z]\b/i;
-  var numbers = /^([\da-f]+h|[0-7]+o|[01]+b|\d+d?)\b/i;
-
-  return {
-    startState: function() {
-      return {
-        context: 0
-      };
-    },
-    token: function(stream, state) {
-      if (!stream.column()) {
-        state.context = 0;
-        if (stream.eatWhile(/[\w.]/))
-          return 'tag';
-      }
-      if (stream.eatSpace())
-        return null;
-
-      var w;
-      if (stream.eatWhile(/\w/)) {
-        w = stream.current();
-        var cur = w.toLowerCase();
-        var style = directives.get(cur);
-        if (style)
-          return style;
-
-        if (opcodes.test(w)) {
-          state.context = 4;
-          return 'keyword';
-        } else if (state.context == 4 && numbers.test(w)) {
-          return 'number';
-        } else if (stream.match(numbers)) {
-          return 'number';
-        } else {
-          return null;
-        }
-      } else if (stream.eat(';')) {
-        stream.skipToEnd();
-        return 'comment';
-      } else if (stream.eat('"')) {
-        while (w = stream.next()) {
-          if (w == '"')
-            break;
-
-          if (w == '\\')
-            stream.next();
-        }
-        return 'string';
-      } else if (stream.eat('\'')) {
-        if (stream.match(/\\?.'/))
-          return 'number';
-      } else if (stream.eat('$') || stream.eat('#')) {
-        if (stream.eatWhile(/[^;]/i))
-          return 'number';
-      } else if (stream.eat('%')) {
-        if (stream.eatWhile(/[01]/))
-          return 'number';
-      } else {
-        stream.next();
-      }
-      return null;
-    }
-  };
-});
-
-CodeMirror.defineMIME("text/x-6502", "6502");
-
-});
diff --git a/src/parser/lang-6502.ts b/src/parser/lang-6502.ts
new file mode 100644
index 00000000..4791f843
--- /dev/null
+++ b/src/parser/lang-6502.ts
@@ -0,0 +1,96 @@
+// CodeMirror 6 language support for 6502 assembly
+// Migrated from CodeMirror 5 mode
+// Original copyright (c) by Marijn Haverbeke and others
+// Distributed under an MIT license: https://codemirror.net/5/LICENSE
+
+import { StreamLanguage, StreamParser } from "@codemirror/language";
+import { LanguageSupport } from "@codemirror/language";
+
+// TODO: Migrate to CodeMirror 6 Lezer parser.
+const asm6502Parser: StreamParser<{ context: number }> = {
+  startState() {
+    return {
+      context: 0
+    };
+  },
+
+  token(stream, state) {
+    // Labels at start of line
+    if (!stream.column()) {
+      state.context = 0;
+      if (stream.eatWhile(/[\w.]/))
+        return 'labelName';
+    }
+
+    if (stream.eatSpace())
+      return null;
+
+    var w;
+    if (stream.eatWhile(/\w/)) {
+      w = stream.current();
+      var cur = w.toLowerCase();
+
+      // Check for directives
+      var style = directives.get(cur);
+      if (style)
+        return style;
+
+      // Check for opcodes (3-letter mnemonics)
+      if (opcodes.test(w)) {
+        state.context = 4;
+        return 'keyword';
+      } else if (state.context == 4 && numbers.test(w)) {
+        return 'number';
+      } else if (stream.match(numbers)) {
+        return 'number';
+      } else {
+        return null;
+      }
+    } else if (stream.eat(';')) {
+      stream.skipToEnd();
+      return 'comment';
+    } else if (stream.eat('"')) {
+      while (w = stream.next()) {
+        if (w == '"')
+          break;
+
+        if (w == '\\')
+          stream.next();
+      }
+      return 'string';
+    } else if (stream.eat('\'')) {
+      if (stream.match(/\\?.'/) || stream.match(/\\?.'/))
+        return 'number';
+    } else if (stream.eat('$') || stream.eat('#')) {
+      if (stream.eatWhile(/[^;]/i))
+        return 'number';
+    } else if (stream.eat('%')) {
+      if (stream.eatWhile(/[01]/))
+        return 'number';
+    } else {
+      stream.next();
+    }
+    return null;
+  }
+};
+
+// Directive keywords
+const directives_list = [
+  'processor',
+  'byte', 'word', 'long',
+  'include', 'seg', 'dc', 'ds', 'dv', 'hex', 'err', 'org', 'rorg', 'echo', 'rend',
+  'align', 'subroutine', 'equ', 'eqm', 'set', 'mac', 'endm', 'mexit', 'ifconst',
+  'ifnconst', 'if', 'else', 'endif', 'eif', 'repeat', 'repend'
+];
+const directives = new Map<string, string>();
+directives_list.forEach(function (s) { directives.set(s, 'keyword'); });
+
+const opcodes = /^[a-z][a-z][a-z]\b/i;
+const numbers = /^([\da-f]+h|[0-7]+o|[01]+b|\d+d?)\b/i;
+
+/**
+ * Language support for 6502 assembly language
+ */
+export function asm6502(): LanguageSupport {
+  return new LanguageSupport(StreamLanguage.define(asm6502Parser));
+}