diff --git a/src/unix.rs b/src/unix.rs
index f0a4321..709bb80 100644
--- a/src/unix.rs
+++ b/src/unix.rs
@@ -136,8 +136,14 @@ impl PktInfoUdpSocket {
         let mut addr_src: MaybeUninit<libc::sockaddr_storage> = MaybeUninit::uninit();
         let mut msg_iov = IoSliceMut::new(buf);
         let mut cmsg = {
-            let space = unsafe {
-                libc::CMSG_SPACE(mem::size_of::<libc::in_pktinfo>() as libc::c_uint) as usize
+            let space = if self.domain == Domain::IPV4 {
+                unsafe {
+                    libc::CMSG_SPACE(mem::size_of::<libc::in_pktinfo>() as libc::c_uint) as usize
+                }
+            } else {
+                unsafe {
+                    libc::CMSG_SPACE(mem::size_of::<libc::in6_pktinfo>() as libc::c_uint) as usize
+                }
             };
             Vec::<u8>::with_capacity(space)
         };
diff --git a/tests/ipv6_test.rs b/tests/ipv6_test.rs
index f16c396..ffd771b 100644
--- a/tests/ipv6_test.rs
+++ b/tests/ipv6_test.rs
@@ -70,6 +70,7 @@ fn ipv6_test() -> io::Result<()> {
         "Multicast packet received on interface index {} from src {} with destination ip {}",
         info.if_index, info.addr_src, info.addr_dst,
     );
+    assert!(info.if_index != 0);
 
     Ok(())
 }