diff --git a/scripts/base/init-bare.zeek b/scripts/base/init-bare.zeek
index 277bab9cc0..b5a629d9ad 100644
--- a/scripts/base/init-bare.zeek
+++ b/scripts/base/init-bare.zeek
@@ -4989,12 +4989,10 @@ export {
 		## of ``127.0.0.1`` or ``[::1]`` are used by loopback interfaces.
 		is_loopback: bool;
 		
-		extended_flags: bool &default=F;
-		# If the "extended_flags" field is set to T, then these next two 
-		# flags will have valid settings.  Otherwise, the following
-		# two fields are explicitly false.
-		is_up: bool &default=F;
-		is_running: bool &default=F;
+		## Whether the device is up.  Not set when that info is unavailable.
+		is_up: bool &optional;
+		## Whether the device is running.  Not set when that info is unavailable.
+		is_running: bool &optional;
 	};
 
 	type Interfaces: set[Pcap::Interface];
diff --git a/src/iosource/pcap/pcap.bif b/src/iosource/pcap/pcap.bif
index 089c77779b..b694330bc7 100644
--- a/src/iosource/pcap/pcap.bif
+++ b/src/iosource/pcap/pcap.bif
@@ -111,11 +111,17 @@ function findalldevs%(%): Pcap::Interfaces
 	pcap_if_t *alldevs, *d;
 	char errbuf[PCAP_ERRBUF_SIZE];
 
-	int ret = pcap_findalldevs(&alldevs, errbuf);
-
 	static auto ifaces_type = id::find_type<TableType>("Pcap::Interfaces");
 	auto pcap_interfaces = make_intrusive<TableVal>(ifaces_type);
 
+	int ret = pcap_findalldevs(&alldevs, errbuf);
+	if ( ret == PCAP_ERROR )
+		{
+		emit_builtin_error(util::fmt("Error calling pcap_findalldevs: %s", errbuf));
+		// Return an empty set in case of failure.
+		return pcap_interfaces;
+		}
+
 	static auto iface_type = id::find_type<RecordType>("Pcap::Interface");
 	for ( d=alldevs; d; d=d->next )
 		{
@@ -142,9 +148,9 @@ function findalldevs%(%): Pcap::Interfaces
 		r->Assign(2, addrs->ToSetVal());
 		r->Assign(3, val_mgr->Bool(d->flags & PCAP_IF_LOOPBACK));
 #ifdef PCAP_IF_UP
-		r->Assign(4, val_mgr->True()); // <-- "extended" vals set.
-		r->Assign(5, val_mgr->Bool(d->flags & PCAP_IF_UP));
-		r->Assign(6, val_mgr->Bool(d->flags & PCAP_IF_RUNNING));
+		// These didn't become available until libpcap 1.6.1
+		r->Assign(4, val_mgr->Bool(d->flags & PCAP_IF_UP));
+		r->Assign(5, val_mgr->Bool(d->flags & PCAP_IF_RUNNING));
 #endif
 		
 		pcap_interfaces->Assign(std::move(r), nullptr);