diff --git a/README.asciidoc b/README.asciidoc
index 921aa41..d83a270 100644
--- a/README.asciidoc
+++ b/README.asciidoc
@@ -729,6 +729,10 @@ ARK server options:
     the `-StructureDestructionTag=DestroySwampSnowStructures`
     option.
 
+`arkNoPortDecrement="<bool>"`::
+    True if the `Port` option should be passed untouched.
+    False for the old behaviour of decrementing the `Port`.
+
 Instance config files
 ~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/tools/arkmanager b/tools/arkmanager
index 75efdc1..6d19e8b 100755
--- a/tools/arkmanager
+++ b/tools/arkmanager
@@ -1100,7 +1100,7 @@ doRun() {
         # Port is actually one higher than specified
         # i.e. specifying port 7777 will have the server
         # use port 7778
-        if [ "$name" == "Port" ]; then
+        if [[ "$name" == "Port" && ( -z "$arkNoPortDecrement" || "$arkNoPortDecrement" == "false" ) ]]; then
           (( val = val - 1 ))
         fi
 
diff --git a/tools/arkmanager.cfg b/tools/arkmanager.cfg
index e1d974d..1ec77b8 100644
--- a/tools/arkmanager.cfg
+++ b/tools/arkmanager.cfg
@@ -17,6 +17,7 @@ arkserverexec="ShooterGame/Binaries/Linux/ShooterGameServer"        # name of AR
 arkbackupdir="/home/steam/ARK-Backups"                              # path to backup directory
 arkwarnminutes="60"                                                 # number of minutes to warn players when using update --warn
 arkprecisewarn="false"                                              # set this to true to obey warnminutes even if no players are connected (recommended for clusters)
+arkNoPortDecrement="true"                                           # unset this to use the old Port - 1 behaviour
 arkautorestartfile="ShooterGame/Saved/.autorestart"                 # path to autorestart file
 arkAutoUpdateOnStart="false"                                        # set this to true if you want to always update before startup
 arkBackupPreUpdate="false"                                          # set this to true if you want to perform a backup before updating