diff --git a/src/test/XSS_test.js b/src/test/XSS_test.js
index f11d60f..e2da8d7 100644
--- a/src/test/XSS_test.js
+++ b/src/test/XSS_test.js
@@ -33,4 +33,37 @@ if (UA.isMozilla) {
       () => y("https://vulnerabledoma.in/xss_link?url=javascript:\\u{%0A6e}ame"),
       ].map(t => Test.run(t))
     ).then(() => Test.report());
+
+    let invalidCharsTest =  async () => {
+
+      await include("xss/InjectionChecker.js");
+      let IC = await XSS.InjectionChecker;
+      let rx = new IC().invalidCharsRx;
+
+      let x = n => '\\u' + ("0000" + n.toString(16)).slice(-4);
+      function check(ch) {
+       eval(`{let _${ch}_}`);
+      }
+      let cur = 0x7e;
+      let fail = false;
+      while (cur++ < 0xffff) {
+        let ch = String.fromCharCode(cur);
+        try {
+          check(ch);
+          if (tx.test(ch)) {
+            console.error(x(cur) + " should not test invalid!");
+            fail = true;
+          }
+        } catch (e) {
+          if (!/illegal char/.test(e.message)) continue;
+          if (!rx.test(ch)) {
+            console.error(x(cur) + " must test invalid!");
+            fail = true;
+          }
+        }
+      }
+      return !fail;
+    };
+
+    Test.run(invalidCharsTest, "InjectionChecker.invalidCharsRx").then(Test.report());
 }
diff --git a/src/xss/InjectionChecker.js b/src/xss/InjectionChecker.js
index 7334ea6..1c99611 100644
--- a/src/xss/InjectionChecker.js
+++ b/src/xss/InjectionChecker.js
@@ -492,43 +492,8 @@ XSS.InjectionChecker = (async () => {
       return ret;
     },
 
-    _createInvalidRanges: function() {
-      function x(n) {
-        return '\\u' + ("0000" + n.toString(16)).slice(-4);
-      }
-
-      let chunks = [];
-      let first = -1;
-      let last = -1;
-      let cur = 0x7e;
-      while (cur++ <= 0xffff) {
-        try {
-          Function("let _" + String.fromCharCode(cur));
-        } catch (e) {
-          if (!/illegal char/.test(e.message)) continue;
-          if (first == -1) {
-            first = last = cur;
-            chunks.push(x(cur));
-            continue;
-          }
-          if (cur - last == 1) {
-            last = cur;
-            continue;
-          }
-
-          if (last != first) chunks.push(`-${x(last)}`);
-          chunks.push(x(cur));
-          last = first = cur;
-        }
-      }
-      return chunks.join('');
-    },
-
-    get invalidCharsRx() {
-      let value = new RegExp("^[^\"'`/<>]*[" + this._createInvalidRanges() + "]");
-      Object.defineProperty(Object.getPrototypeOf(this), 'invalidCharsRx', {value});
-      return value;
-    },
+    // see https://mathiasbynens.be/notes/javascript-identifiers-es6#acceptable-unicode-symbols
+    invalidCharsRx: /^[^"'`/<>]*[^$_\p{ID_Start}\p{ID_Continue}\u200c\u200d]/u,
 
     async checkJSBreak(s) {
       // Direct script injection breaking JS string literals or comments