diff --git a/src/graph.c b/src/graph.c
index 25ff22a9..46f4bc98 100644
--- a/src/graph.c
+++ b/src/graph.c
@@ -249,9 +249,9 @@ static void check_reachability(void) {
 			char *port;
 			char *envp[8] = {NULL};
 
-			xasprintf(&envp[0], "NETNAME=%s", netname ? netname : "");
-			xasprintf(&envp[1], "DEVICE=%s", device ? device : "");
-			xasprintf(&envp[2], "INTERFACE=%s", iface ? iface : "");
+			xasprintf(&envp[0], "NETNAME=%s", netname ? : "");
+			xasprintf(&envp[1], "DEVICE=%s", device ? : "");
+			xasprintf(&envp[2], "INTERFACE=%s", iface ? : "");
 			xasprintf(&envp[3], "NODE=%s", n->name);
 			sockaddr2str(&n->address, &address, &port);
 			xasprintf(&envp[4], "REMOTEADDRESS=%s", address);