diff --git a/src/network/networkd-network.h b/src/network/networkd-network.h
index 17cff956dae..4dbc19fc3b6 100644
--- a/src/network/networkd-network.h
+++ b/src/network/networkd-network.h
@@ -174,7 +174,7 @@ struct Network {
         IPv6PrivacyExtensions ipv6_privacy_extensions;
 
         struct ether_addr *mac;
-        unsigned mtu;
+        size_t mtu;
         int arp;
         uint32_t iaid;
         DUID duid;