diff --git a/bitpacker/src/blocked_bitpacker.rs b/bitpacker/src/blocked_bitpacker.rs
index 271ab7f67..027886dfb 100644
--- a/bitpacker/src/blocked_bitpacker.rs
+++ b/bitpacker/src/blocked_bitpacker.rs
@@ -1,4 +1,4 @@
-use crate::BitUnpacker;
+use crate::{minmax, BitUnpacker};
 
 use super::{bitpacker::BitPacker, compute_num_bits};
 
@@ -83,14 +83,9 @@ impl BlockedBitpacker {
     }
 
     pub fn flush(&mut self) {
-        if let Some(min_value) = self.buffer.iter().min() {
+        if let Some((min_value, max_value)) = minmax(self.buffer.iter()) {
             let mut bit_packer = BitPacker::new();
-            let num_bits_block = self
-                .buffer
-                .iter()
-                .map(|val| compute_num_bits(*val - min_value))
-                .max()
-                .unwrap();
+            let num_bits_block = compute_num_bits(*max_value - min_value);
             // todo performance: the padding handling could be done better, e.g. use a slice and
             // return num_bytes written from bitpacker
             self.compressed_blocks
diff --git a/bitpacker/src/lib.rs b/bitpacker/src/lib.rs
index cb566769c..1697a8488 100644
--- a/bitpacker/src/lib.rs
+++ b/bitpacker/src/lib.rs
@@ -37,3 +37,16 @@ pub fn compute_num_bits(n: u64) -> u8 {
         64
     }
 }
+
+pub fn minmax<I, T>(mut vals: I) -> Option<(T, T)>
+where
+    I: Iterator<Item = T>,
+    T: Copy + Ord,
+{
+    if let Some(first_el) = vals.next() {
+        return Some(vals.fold((first_el, first_el), |(min_val, max_val), el| {
+            (min_val.min(el), max_val.max(el))
+        }));
+    }
+    None
+}
diff --git a/src/common/mod.rs b/src/common/mod.rs
index 43ea7be51..bfa3b1262 100644
--- a/src/common/mod.rs
+++ b/src/common/mod.rs
@@ -19,19 +19,6 @@ pub use byteorder::LittleEndian as Endianness;
 /// We do not allow segments with more than
 pub const MAX_DOC_LIMIT: u32 = 1 << 31;
 
-pub fn minmax<I, T>(mut vals: I) -> Option<(T, T)>
-where
-    I: Iterator<Item = T>,
-    T: Copy + Ord,
-{
-    if let Some(first_el) = vals.next() {
-        return Some(vals.fold((first_el, first_el), |(min_val, max_val), el| {
-            (min_val.min(el), max_val.max(el))
-        }));
-    }
-    None
-}
-
 /// Has length trait
 pub trait HasLen {
     /// Return length
@@ -116,12 +103,12 @@ pub fn u64_to_f64(val: u64) -> f64 {
 #[cfg(test)]
 pub(crate) mod test {
 
-    pub use super::minmax;
     pub use super::serialize::test::fixed_size_test;
     use super::{f64_to_u64, i64_to_u64, u64_to_f64, u64_to_i64};
     use proptest::prelude::*;
     use std::f64;
     use tantivy_bitpacker::compute_num_bits;
+    pub use tantivy_bitpacker::minmax;
 
     fn test_i64_converter_helper(val: i64) {
         assert_eq!(u64_to_i64(i64_to_u64(val)), val);
diff --git a/src/fastfield/multivalued/writer.rs b/src/fastfield/multivalued/writer.rs
index e7c2bc409..b25888e78 100644
--- a/src/fastfield/multivalued/writer.rs
+++ b/src/fastfield/multivalued/writer.rs
@@ -8,6 +8,7 @@ use crate::DocId;
 use fnv::FnvHashMap;
 use std::io;
 use std::iter::once;
+use tantivy_bitpacker::minmax;
 
 /// Writer for multi-valued (as in, more than one value per document)
 /// int fast field.
@@ -154,7 +155,7 @@ impl MultiValuedFastFieldWriter {
                     }
                 }
                 None => {
-                    let val_min_max = crate::common::minmax(self.vals.iter().cloned());
+                    let val_min_max = minmax(self.vals.iter().cloned());
                     let (val_min, val_max) = val_min_max.unwrap_or((0u64, 0u64));
                     value_serializer =
                         serializer.new_u64_fast_field_with_idx(self.field, val_min, val_max, 1)?;
diff --git a/src/indexer/merger.rs b/src/indexer/merger.rs
index 93099b50c..6004d2984 100644
--- a/src/indexer/merger.rs
+++ b/src/indexer/merger.rs
@@ -1,3 +1,5 @@
+use tantivy_bitpacker::minmax;
+
 use crate::common::MAX_DOC_LIMIT;
 use crate::core::Segment;
 use crate::core::SegmentReader;
@@ -70,7 +72,7 @@ fn compute_min_max_val(
             Some(delete_bitset) => {
                 // some deleted documents,
                 // we need to recompute the max / min
-                crate::common::minmax(
+                minmax(
                     (0..max_doc)
                         .filter(|doc_id| delete_bitset.is_alive(*doc_id))
                         .map(|doc_id| u64_reader.get(doc_id)),