diff --git a/code/include/swoc/IPAddr.h b/code/include/swoc/IPAddr.h
index 690ee14..50d14af 100644
--- a/code/include/swoc/IPAddr.h
+++ b/code/include/swoc/IPAddr.h
@@ -579,7 +579,7 @@ class IPAddr {
    * @param sa Destination.
    * @return @a sa
    */
-  sockaddr *copy_to(sockaddr *sa);
+  sockaddr *copy_to(sockaddr *sa) const;
 
   /** Parse a string and load the result in @a this.
    *
diff --git a/code/src/swoc_ip.cc b/code/src/swoc_ip.cc
index 67fc9fa..0ddc9bb 100644
--- a/code/src/swoc_ip.cc
+++ b/code/src/swoc_ip.cc
@@ -515,7 +515,7 @@ IPAddr::operator=(IPEndpoint const &addr) {
 }
 
 sockaddr *
-IPAddr::copy_to(sockaddr *sa) {
+IPAddr::copy_to(sockaddr *sa) const {
   if (this->is_ip4()) {
     _addr._ip4.copy_to(sa);
   } else if (this->is_ip6()) {