Index: contrib/tcpdump/tcpdump.c
===================================================================
--- contrib/tcpdump/tcpdump.c
+++ contrib/tcpdump/tcpdump.c
@@ -1915,7 +1915,7 @@
 	if (pcap_setfilter(pd, &fcode) < 0)
 		error("%s", pcap_geterr(pd));
 #ifdef HAVE_CAPSICUM
-	if (RFileName == NULL && VFileName == NULL) {
+	if (RFileName == NULL && VFileName == NULL && pcap_fileno(pd) != -1) {
 		static const unsigned long cmds[] = { BIOCGSTATS, BIOCROTZBUF };
 
 		/*
@@ -2069,6 +2069,9 @@
 #else
 	cansandbox = (cansandbox && ndo->ndo_nflag);
 #endif	/* HAVE_CASPER */
+	cansandbox = (cansandbox && (pcap_fileno(pd) != -1 ||
+	    RFileName != NULL));
+
 	if (cansandbox && cap_enter() < 0 && errno != ENOSYS)
 		error("unable to enter the capability mode");
 #endif	/* HAVE_CAPSICUM */