diff --git a/benches/parse_bench.rs b/benches/parse_bench.rs
index f206f83..ba2f1c8 100644
--- a/benches/parse_bench.rs
+++ b/benches/parse_bench.rs
@@ -5,6 +5,8 @@ extern crate ipnetwork;
 use ipnetwork::{Ipv4Network, Ipv6Network};
 use criterion::Criterion;
 
+use std::net::{Ipv4Addr, Ipv6Addr};
+
 fn parse_ipv4_benchmark(c: &mut Criterion) {
     c.bench_function("parse ipv4", |b| b.iter(|| {
         "127.1.0.0/24".parse::<Ipv4Network>().unwrap()
@@ -17,5 +19,19 @@ fn parse_ipv6_benchmark(c: &mut Criterion) {
     }));
 }
 
-criterion_group!(benches, parse_ipv4_benchmark, parse_ipv6_benchmark);
+fn contains_ipv4_benchmark(c: &mut Criterion) {
+    c.bench_function("contains ipv4", |b| b.iter(|| {
+        let cidr = "74.125.227.0/25".parse::<Ipv4Network>().unwrap();
+        cidr.contains(Ipv4Addr::new(74, 125, 227, 4))
+    }));
+}
+
+fn contains_ipv6_benchmark(c: &mut Criterion) {
+    c.bench_function("contains ipv6", |b| b.iter(|| {
+        let cidr = "FF01:0:0:17:0:0:0:2/65".parse::<Ipv6Network>().unwrap();
+        cidr.contains(Ipv6Addr::new(0xff01, 0, 0, 0x17, 0x7fff, 0, 0, 0x2))
+    }));
+}
+
+criterion_group!(benches, parse_ipv4_benchmark, parse_ipv6_benchmark, contains_ipv4_benchmark, contains_ipv6_benchmark);
 criterion_main!(benches);
diff --git a/src/ipv4.rs b/src/ipv4.rs
index 67f49d7..ec4fa27 100644
--- a/src/ipv4.rs
+++ b/src/ipv4.rs
@@ -131,8 +131,8 @@ impl Ipv4Network {
     /// assert!(!net.contains(Ipv4Addr::new(127, 0, 1, 70)));
     /// ```
     pub fn contains(&self, ip: Ipv4Addr) -> bool {
-        let net = u32::from(self.network());
-        let mask = u32::from(self.mask());
+        let mask = !(0xffff_ffff as u64 >> self.prefix) as u32;
+        let net = u32::from(self.addr) & mask;
         (u32::from(ip) & mask) == net
     }