diff --git a/src/core/core_utils.js b/src/core/core_utils.js
index 5556c9e15..bbc7ef735 100644
--- a/src/core/core_utils.js
+++ b/src/core/core_utils.js
@@ -533,7 +533,7 @@ function encodeToXmlString(str) {
         buffer.push(str.substring(start, i));
       }
       buffer.push(`&#x${char.toString(16).toUpperCase()};`);
-      if (char > 0xd7ff && (char < 0xe000 || char > 0xfffd)) {
+      if (char > 0xffff) {
         // char is represented by two u16
         i++;
       }
diff --git a/test/unit/core_utils_spec.js b/test/unit/core_utils_spec.js
index a9c6bd8f0..597f2cfbf 100644
--- a/test/unit/core_utils_spec.js
+++ b/test/unit/core_utils_spec.js
@@ -312,6 +312,11 @@ describe("core_utils", function () {
       const str = "hello world";
       expect(encodeToXmlString(str)).toEqual(str);
     });
+
+    it("should keep the character after U+FFFE or U+FFFF", function () {
+      expect(encodeToXmlString("￿A")).toEqual("&#xFFFF;A");
+      expect(encodeToXmlString("￾B")).toEqual("&#xFFFE;B");
+    });
   });
 
   describe("validateCSSFont", function () {