diff --git a/arch/sandbox/cpu/eth-raw-os.c b/arch/sandbox/cpu/eth-raw-os.c
index e054a07..61f23ed 100644
--- a/arch/sandbox/cpu/eth-raw-os.c
+++ b/arch/sandbox/cpu/eth-raw-os.c
@@ -156,7 +156,7 @@
 	int retval;
 	struct udphdr *udph = packet + sizeof(struct iphdr);
 
-	if (!priv->sd || !priv->device)
+	if (priv->sd < 0 || !priv->device)
 		return -EINVAL;
 
 	/*
@@ -221,7 +221,7 @@
 	int retval;
 	int saddr_size;
 
-	if (!priv->sd || !priv->device)
+	if (priv->sd < 0 || !priv->device)
 		return -EINVAL;
 	saddr_size = sizeof(struct sockaddr);
 	retval = recvfrom(priv->sd, packet, 1536, 0,