Note that we might not get an interface drop count from /proc/net/dev.
diff --git a/pcap-linux.c b/pcap-linux.c
index d2f7c51..aeae6de 100644
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -1723,7 +1723,8 @@
 	 *	"ps_drop" is not supported.
 	 *
 	 *	"ps_ifdrop" is supported. It will return the number
-	 *	of drops the interface reports in /proc/net/dev
+	 *	of drops the interface reports in /proc/net/dev,
+	 *	if that is available.
 	 *
 	 *	"ps_recv" doesn't include packets not yet read from
 	 *	the kernel by libpcap.