diff --git a/common/src/main/scala/net/psforever/packet/game/ZoneInfoMessage.scala b/common/src/main/scala/net/psforever/packet/game/ZoneInfoMessage.scala
index 09e84c7d..c1c4b7a6 100644
--- a/common/src/main/scala/net/psforever/packet/game/ZoneInfoMessage.scala
+++ b/common/src/main/scala/net/psforever/packet/game/ZoneInfoMessage.scala
@@ -6,18 +6,22 @@ import scodec.Codec
 import scodec.codecs._
 
 /**
-  * na
+  * Change the "Empire Status" text in the Interstellar Map zone description for the specified zone.<br>
+  * <br>
+  * The `Long` value is applicable to the caverns.
+  * It indicates how long the given cavern will remain locked until at least one of their geowarps will open during normal rotation.
+  * As thus, when a cavern has its status as "inactive," this number will always be a non-zero.
+  * On normal continents, this number is always zero, though a non-zero number will not have any effect anyway.
   * @param zone the zone id
-  * @param empire_status change the "Empire Status" text in the Interstellar Map zone description;
-  *                      `true` displays the queue availability for the avatar's empire;
-  *                      `false` display "Inactive"
-  * @param unk na;
-  *            always 0?
-  * @see `ZonePopulationUpdateMessage`
+  * @param empire_status `true` displays the queue availability for the avatar's empire;
+  *                      `false` displays "Inactive"
+  * @param lock_time how long until the continent naturally unlocks (in ms);
+  *                  only applicable to caverns
+  * @see `ZonePopulationUpdateMessage` for information on population and queues
   */
 final case class ZoneInfoMessage(zone : Int,
                                  empire_status : Boolean,
-                                 unk : Long)
+                                 lock_time : Long)
   extends PlanetSideGamePacket {
   type Packet = ZoneInfoMessage
   def opcode = GamePacketOpcode.ZoneInfoMessage
@@ -28,6 +32,6 @@ object ZoneInfoMessage extends Marshallable[ZoneInfoMessage] {
   implicit val codec : Codec[ZoneInfoMessage] = (
     ("zone" | uint16L) ::
       ("empire_status" | bool) ::
-      ("unk" | uint32L)
+      ("lock_time" | uint32L)
     ).as[ZoneInfoMessage]
 }
diff --git a/common/src/test/scala/GamePacketTest.scala b/common/src/test/scala/GamePacketTest.scala
index abb05c7e..903b62f0 100644
--- a/common/src/test/scala/GamePacketTest.scala
+++ b/common/src/test/scala/GamePacketTest.scala
@@ -2184,8 +2184,9 @@ class GamePacketTest extends Specification {
 
     "ZoneInfoMessage" should {
       val string = hex"C6 0C 00 80 00 00 00 00"
+      val string_cavern = hex"C6 1B 00 1D F9 F3 00 00"
 
-      "decode" in {
+      "decode (normal)" in {
         PacketCoding.DecodePacket(string).require match {
           case ZoneInfoMessage(zone, empire_status, unk) =>
             zone mustEqual 12
@@ -2196,12 +2197,30 @@ class GamePacketTest extends Specification {
         }
       }
 
-      "encode" in {
+      "decode (cavern)" in {
+        PacketCoding.DecodePacket(string_cavern).require match {
+          case ZoneInfoMessage(zone, empire_status, unk) =>
+            zone mustEqual 27
+            empire_status mustEqual false
+            unk mustEqual 15135547
+          case default =>
+            ko
+        }
+      }
+
+      "encode (normal)" in {
         val msg = ZoneInfoMessage(12, true, 0)
         val pkt = PacketCoding.EncodePacket(msg).require.toByteVector
 
         pkt mustEqual string
       }
+
+      "encode (cavern)" in {
+        val msg = ZoneInfoMessage(27, false, 15135547)
+        val pkt = PacketCoding.EncodePacket(msg).require.toByteVector
+
+        pkt mustEqual string_cavern
+      }
     }
 
     "PingMsg" should  {