diff --git a/src/ipv4.rs b/src/ipv4.rs
index 5906ef0..15b46d9 100644
--- a/src/ipv4.rs
+++ b/src/ipv4.rs
@@ -144,7 +144,7 @@ impl Ipv4Network {
         self.addr
     }
 
-    pub fn prefix(self) -> u8 {
+    pub const fn prefix(self) -> u8 {
         self.prefix
     }
 
diff --git a/src/ipv6.rs b/src/ipv6.rs
index 2767471..9e70371 100644
--- a/src/ipv6.rs
+++ b/src/ipv6.rs
@@ -164,7 +164,7 @@ impl Ipv6Network {
         self.addr
     }
 
-    pub fn prefix(&self) -> u8 {
+    pub const fn prefix(&self) -> u8 {
         self.prefix
     }
 
diff --git a/src/lib.rs b/src/lib.rs
index 491e7c3..6bc6cb1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -160,7 +160,7 @@ impl IpNetwork {
     /// assert_eq!(IpNetwork::V6("ff01::0".parse().unwrap()).prefix(), 128u8);
     /// assert_eq!(IpNetwork::V6("ff01::0/32".parse().unwrap()).prefix(), 32u8);
     /// ```
-    pub fn prefix(&self) -> u8 {
+    pub const fn prefix(&self) -> u8 {
         match *self {
             IpNetwork::V4(ref a) => a.prefix(),
             IpNetwork::V6(ref a) => a.prefix(),