diff --git a/crates/num-rug-adapter/src/lib.rs b/crates/num-rug-adapter/src/lib.rs
index a95d42c8..6cb19918 100644
--- a/crates/num-rug-adapter/src/lib.rs
+++ b/crates/num-rug-adapter/src/lib.rs
@@ -117,6 +117,11 @@ impl Integer {
     pub fn gcd(&self, other: &Self) -> Self {
         Integer(num_integer::Integer::gcd(&self.0, &other.0))
     }
+
+    #[inline]
+    pub fn count_ones(&self) -> Option<u32> {
+        Some(self.0.to_u32_digits().1.iter().map(|&d| d.count_ones()).sum())
+    }
 }
 
 impl From<&Integer> for Integer {