diff --git a/tts.js b/tts.js
index bf665c5..b53add8 100644
--- a/tts.js
+++ b/tts.js
@@ -22,7 +22,12 @@ const getAlphabet = el => {
 }
 
 const getSegmenter = (lang = 'en', granularity = 'word') => {
-    const segmenter = new Intl.Segmenter(lang, { granularity })
+    // `lang` may be explicitly null when getLang() walks to the document
+    // root without finding a language attribute — common for PDFs, which
+    // almost never declare a language. The default parameter above only
+    // applies when the argument is `undefined`, not `null`, so we need a
+    // separate fallback here to avoid `Intl.Segmenter(null, ...)` throwing.
+    const segmenter = new Intl.Segmenter(lang || 'en', { granularity })
     const granularityIsWord = granularity === 'word'
     return function* (strs, makeRange) {
         const str = strs.join('')
diff --git a/view.js b/view.js
index 7397ea2..6d20e27 100644
--- a/view.js
+++ b/view.js
@@ -585,8 +585,14 @@ export class View extends HTMLElement {
         const doc = this.renderer.getContents()[0].doc
         if (this.tts && this.tts.doc === doc) return
         const { TTS } = await import('./tts.js')
-        this.tts = new TTS(doc, textWalker, highlight || (range =>
-            this.renderer.scrollToAnchor(range, true)), granularity)
+        this.tts = new TTS(doc, textWalker, highlight || (range => {
+            // Not every renderer implements scrollToAnchor — in particular,
+            // the PDF renderer is fixed-layout and has no notion of an
+            // anchor to scroll to. Guard the call so that TTS still works
+            // on PDFs, just without sentence-highlight sync.
+            if (typeof this.renderer.scrollToAnchor === 'function')
+                this.renderer.scrollToAnchor(range, true)
+        }), granularity)
     }
     startMediaOverlay() {
         const { index } = this.renderer.getContents()[0]