diff --git a/components/script/dom/offlineaudiocontext.rs b/components/script/dom/offlineaudiocontext.rs
index 32aaa926ec9..7e967d0078a 100644
--- a/components/script/dom/offlineaudiocontext.rs
+++ b/components/script/dom/offlineaudiocontext.rs
@@ -151,10 +151,14 @@ impl OfflineAudioContextMethods for OfflineAudioContext {
                     task!(resolve: move || {
                         let this = this.root();
                         let processed_audio = processed_audio.lock().unwrap();
-                        let processed_audio: Vec<_> = processed_audio
+                        let mut processed_audio: Vec<_> = processed_audio
                             .chunks(this.length as usize)
                             .map(|channel| channel.to_vec())
                             .collect();
+                        // it can end up being empty if the task failed
+                        if processed_audio.len() != this.length as usize {
+                            processed_audio.resize(this.length as usize, Vec::new())
+                        }
                         let buffer = AudioBuffer::new(
                             &this.global().as_window(),
                             this.channel_count,