diff --git a/src/extensions/scratch3_music/index.js b/src/extensions/scratch3_music/index.js
index 6d661bd24..0e14a2150 100644
--- a/src/extensions/scratch3_music/index.js
+++ b/src/extensions/scratch3_music/index.js
@@ -10,7 +10,14 @@ const Timer = require('../../util/timer');
  * @type {string}
  */
 // eslint-disable-next-line max-len
-const iconURI = 'data:image/svg+xml;base64,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';
+const blockIconURI = 'data:image/svg+xml;base64,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';
+
+/**
+ * Icon svg to be displayed in the category menu, encoded as a data URI.
+ * @type {string}
+ */
+// eslint-disable-next-line max-len
+const menuIconURI = 'data:image/svg+xml;base64,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';
 
 /**
  * Class for the music-related blocks in Scratch 3.0
@@ -402,7 +409,8 @@ class Scratch3MusicBlocks {
         return {
             id: 'music',
             name: 'Music',
-            iconURI: iconURI,
+            menuIconURI: menuIconURI,
+            blockIconURI: blockIconURI,
             blocks: [
                 {
                     opcode: 'playDrumForBeats',
diff --git a/src/extensions/scratch3_pen/index.js b/src/extensions/scratch3_pen/index.js
index e194a1d50..b3a8818d3 100644
--- a/src/extensions/scratch3_pen/index.js
+++ b/src/extensions/scratch3_pen/index.js
@@ -13,7 +13,7 @@ const log = require('../../util/log');
  * @type {string}
  */
 // eslint-disable-next-line max-len
-const iconURI = 'data:image/svg+xml;base64,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';
+const blockIconURI = 'data:image/svg+xml;base64,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';
 
 /**
  * Enum for pen color parameter values.
@@ -286,7 +286,7 @@ class Scratch3PenBlocks {
         return {
             id: 'pen',
             name: 'Pen',
-            iconURI: iconURI,
+            blockIconURI: blockIconURI,
             blocks: [
                 {
                     opcode: 'clear',