diff --git a/sbin/packet-capture.sh b/sbin/packet-capture.sh
index 37c9bb6..af6eab1 100755
--- a/sbin/packet-capture.sh
+++ b/sbin/packet-capture.sh
@@ -16,7 +16,12 @@ OUTPATH="$OUTDIR/$OUTNAME"
 # 30000/UDP: Navigation system headers
 # Not all inputs will be present in all systems.
 #
-EXPR="udp and (port 4461 or port 4462 or port 30000)"
+# NOTE: $INS_HOST must be defined and point to the
+# navigation server. The reason we don't use a port
+# filter for this data is because that doesn't work
+# with fragmented UDP packets.
+#
+EXPR="udp and (port 4461 or port 4462 or src host $INS_HOST)"
 
 if [[ ! -d "$OUTDIR" ]]; then
     mkdir "$OUTDIR"