diff --git a/.github/workflows/icu4j.yml b/.github/workflows/icu4j.yml
index 868f3dd8bc9b..538725ba7172 100644
--- a/.github/workflows/icu4j.yml
+++ b/.github/workflows/icu4j.yml
@@ -67,7 +67,7 @@ jobs:
         run: |
           cd icu4j;
           mvn ${SHARED_MVN_ARGS} dependency:go-offline -P '!old_jdk_taglet'
-          
+
   # ICU4J build and unit test using Maven
   # https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-java-with-maven
   icu4j-mvn-build-and-test:
@@ -75,7 +75,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java-version: [ '8', '11', '17' ]
+        java-version: [ '8', '11', '17', '21' ]
     runs-on: ubuntu-latest
     steps:
       - name: Checkout and setup
diff --git a/testdata/message2/more-functions.json b/testdata/message2/more-functions.json
index 83a55151f786..b34803635ce9 100644
--- a/testdata/message2/more-functions.json
+++ b/testdata/message2/more-functions.json
@@ -102,19 +102,10 @@
     },
     {
       "src": "Default int64: {$val}!",
-      "exp": "Default int64: 1.234.567.890.123.456.800!",
+      "exp": "Default int64: 1.234.567.890.123.456.789!",
       "locale": "ro",
-      "params": [{ "name": "val", "value": 1234567890123456789 }],
-      "comment": "Rounded due to JSON not supporting full 64-bit ints",
-      "ignoreJava": "See https://unicode-org.atlassian.net/browse/ICU-22754?focusedCommentId=175932"
-    },
-    {
-      "src": "Default int64: {$val}!",
-      "exp": "Default int64: 1.234.567.890.123.456.770!",
-      "locale": "ro",
-      "params": [{ "name": "val", "value": 1234567890123456789 }],
-      "comment": "Rounded due to JSON not supporting full 64-bit ints",
-      "ignoreCpp": "See https://unicode-org.atlassian.net/browse/ICU-22754?focusedCommentId=175932"
+      "params": [{ "name": "val", "value": {"decimal": "1234567890123456789"} }],
+      "comment": "Rounded due to JSON not supporting full 64-bit ints"
     },
     {
       "src": "Default number: {$val}!",