diff --git a/src/extensions/scratch3_pen/index.js b/src/extensions/scratch3_pen/index.js
index 16c09dfb61..b1b8eace4a 100644
--- a/src/extensions/scratch3_pen/index.js
+++ b/src/extensions/scratch3_pen/index.js
@@ -298,6 +298,16 @@ class Scratch3PenBlocks {
             }),
             blockIconURI: blockIconURI,
             blocks: [
+                // tw: additional message when on the stage for clarity
+                {
+                    blockType: BlockType.LABEL,
+                    text: formatMessage({
+                        id: 'tw.pen.stageSelected',
+                        default: 'Stage selected: less pen blocks',
+                        description: 'Label that appears in the Pen category when the stage is selected'
+                    }),
+                    filter: [TargetType.STAGE]
+                },
                 {
                     opcode: 'clear',
                     blockType: BlockType.COMMAND,
diff --git a/src/util/base64-util.js b/src/util/base64-util.js
index 1325291707..19165c980b 100644
--- a/src/util/base64-util.js
+++ b/src/util/base64-util.js
@@ -20,10 +20,13 @@ class Base64Util {
 
     /**
      * Convert a Uint8Array to a base64 encoded string.
-     * @param {Uint8Array} array - the array to convert.
+     * @param {Uint8Array|Array<number>} array - the array to convert.
      * @return {string} - the base64 encoded string.
      */
     static uint8ArrayToBase64 (array) {
+        if (Array.isArray(array)) {
+            array = new Uint8Array(array);
+        }
         let binary = '';
         const len = array.byteLength;
         for (let i = 0; i < len; i++) {
diff --git a/test/unit/util_base64.js b/test/unit/util_base64.js
index c18c353333..f43aa14859 100644
--- a/test/unit/util_base64.js
+++ b/test/unit/util_base64.js
@@ -3,6 +3,7 @@ const Base64Util = require('../../src/util/base64-util');
 
 test('uint8ArrayToBase64', t => {
     t.equal(Base64Util.uint8ArrayToBase64(new Uint8Array([0, 50, 80, 200])), 'ADJQyA==');
+    t.equal(Base64Util.uint8ArrayToBase64([0, 50, 80, 200]), 'ADJQyA==');
     t.end();
 });
 
@@ -25,11 +26,13 @@ test('round trips', t => {
         new Uint8Array(0),
         new Uint8Array([10, 90, 0, 255, 255, 255, 10, 2]),
         new Uint8Array(10000),
-        new Uint8Array(1000000)
+        new Uint8Array(100000)
     ];
     for (const uint8array of data) {
         const uint8ToBase64 = Base64Util.uint8ArrayToBase64(uint8array);
+        const arrayToBase64 = Base64Util.uint8ArrayToBase64(Array.from(uint8array));
         const bufferToBase64 = Base64Util.arrayBufferToBase64(uint8array.buffer);
+        t.equal(uint8ToBase64, arrayToBase64);
         t.equal(uint8ToBase64, bufferToBase64);
         const decoded = Base64Util.base64ToUint8Array(uint8ToBase64);
         t.same(uint8array, decoded);