diff --git a/crates/frender-ssr/src/bytes/sliced.rs b/crates/frender-ssr/src/bytes/sliced.rs
index 7ad2e70a..e641c639 100644
--- a/crates/frender-ssr/src/bytes/sliced.rs
+++ b/crates/frender-ssr/src/bytes/sliced.rs
@@ -21,7 +21,7 @@ impl AsRef<[u8]> for SlicedBytes {
 
 impl super::AsyncWritableBytes for SlicedBytes {
     fn truncate_start_at(&mut self, n: usize) {
-        assert!(n < self.inner.len());
+        assert!(n + self.start <= self.inner.len());
         self.start += n;
     }
 }