diff --git a/js/accessibility/voicing/InteractiveHighlighting.ts b/js/accessibility/voicing/InteractiveHighlighting.ts
index c721e1e34..a89353392 100644
--- a/js/accessibility/voicing/InteractiveHighlighting.ts
+++ b/js/accessibility/voicing/InteractiveHighlighting.ts
@@ -31,6 +31,7 @@ type InteractiveHighlightingOptions = InteractiveHighlightingSelfOptions & NodeO
  * @param optionsArgPosition - zero-indexed number that the options argument is provided at
  */
 const InteractiveHighlighting = <SuperType extends Constructor>( Type: SuperType, optionsArgPosition: number ) => {
+  assert && assert( typeof optionsArgPosition === 'number', 'Must provide an index to access options arg from (zero-indexed)' );
   assert && assert( _.includes( inheritance( Type ), Node ), 'Only Node subtypes should compose InteractiveHighlighting' );
 
   const InteractiveHighlightingClass = class extends Type {
diff --git a/js/accessibility/voicing/ReadingBlockNode.js b/js/accessibility/voicing/ReadingBlockNode.js
index 4003b370c..60915503c 100644
--- a/js/accessibility/voicing/ReadingBlockNode.js
+++ b/js/accessibility/voicing/ReadingBlockNode.js
@@ -17,7 +17,7 @@
 import merge from '../../../../phet-core/js/merge.js';
 import { scenery, Node, ReadingBlock, ReadingBlockHighlight } from '../../imports.js';
 
-class ReadingBlockNode extends ReadingBlock( Node ) {
+class ReadingBlockNode extends ReadingBlock( Node, 0 ) {
 
   /**
    * @param {Object} [options]
diff --git a/js/accessibility/voicing/nodes/VoicingRichText.js b/js/accessibility/voicing/nodes/VoicingRichText.js
index 55b6cb6da..bc7ee7c33 100644
--- a/js/accessibility/voicing/nodes/VoicingRichText.js
+++ b/js/accessibility/voicing/nodes/VoicingRichText.js
@@ -10,7 +10,7 @@
 import merge from '../../../../../phet-core/js/merge.js';
 import { ReadingBlock, ReadingBlockHighlight, RichText, scenery } from '../../../imports.js';
 
-class VoicingRichText extends ReadingBlock( RichText ) {
+class VoicingRichText extends ReadingBlock( RichText, 1 ) {
 
   /**
    * @param {string} text
diff --git a/js/accessibility/voicing/nodes/VoicingText.js b/js/accessibility/voicing/nodes/VoicingText.js
index 27f5abe9d..138ca6170 100644
--- a/js/accessibility/voicing/nodes/VoicingText.js
+++ b/js/accessibility/voicing/nodes/VoicingText.js
@@ -10,7 +10,7 @@
 import merge from '../../../../../phet-core/js/merge.js';
 import { ReadingBlock, ReadingBlockHighlight, scenery, Text } from '../../../imports.js';
 
-class VoicingText extends ReadingBlock( Text ) {
+class VoicingText extends ReadingBlock( Text, 1 ) {
 
   /**
    * @param {string} text