diff --git a/rs/compression/src/compression.rs b/rs/compression/src/compression.rs
index 232374a..652930a 100644
--- a/rs/compression/src/compression.rs
+++ b/rs/compression/src/compression.rs
@@ -6,7 +6,7 @@ use memmap2::Mmap;
 
 pub trait IntSeqEncoder {
     /// Creates an encoder
-    fn new_encoder(universe: Option<usize>, num_elem: usize) -> Self
+    fn new_encoder(universe: usize, num_elem: usize) -> Self
     where
         Self: Sized;
 
diff --git a/rs/compression/src/noc/noc.rs b/rs/compression/src/noc/noc.rs
index e364c49..3bb012d 100644
--- a/rs/compression/src/noc/noc.rs
+++ b/rs/compression/src/noc/noc.rs
@@ -23,7 +23,7 @@ impl PlainEncoder {
 }
 
 impl IntSeqEncoder for PlainEncoder {
-    fn new_encoder(_universe: Option<usize>, num_elem: usize) -> Self {
+    fn new_encoder(_universe: usize, num_elem: usize) -> Self {
         Self::new(num_elem)
     }
 
diff --git a/rs/index/src/ivf/writer.rs b/rs/index/src/ivf/writer.rs
index 968f7ac..bb3eba8 100644
--- a/rs/index/src/ivf/writer.rs
+++ b/rs/index/src/ivf/writer.rs
@@ -188,7 +188,10 @@ impl<Q: Quantizer, C: IntSeqEncoder + 'static> IvfWriter<Q, C> {
                 .get(i as u32)?
                 .iter()
                 .collect::<Vec<_>>();
-            let mut encoder = C::new_encoder(/*universe*/ None, posting_list.len());
+            let mut encoder = C::new_encoder(
+                *posting_list.last().unwrap_or(&0) as usize,
+                posting_list.len(),
+            );
             // Encode to get the length of the encoded data
             encoder.encode(&posting_list)?;
             // Write the length of the encoded posting list