diff --git a/VAX/tests/vax-diag_test.ini b/VAX/tests/vax-diag_test.ini
index 9c73748c..58233c88 100644
--- a/VAX/tests/vax-diag_test.ini
+++ b/VAX/tests/vax-diag_test.ini
@@ -32,7 +32,7 @@ on runtime echof "\r\n*** Test Runtime Limit %SIM_RUNLIMIT% %SIM_RUNLIMIT_UNITS%
 
 :NEXT_ARG
 set env DIAG_QUIET_MODE=0
-set env -A TELNET_PORT=(65300+TIME_SS)
+set env -A TELNET_PORT=(60000+((TIME_SS+SIM_PROCESS_PID)%5200))
 if ("%1" == "-v") set console notelnet;shift
 else set -qu console telnet=localhost:%TELNET_PORT%,telnet=buffered=1048576; set env -a DIAG_QUIET_MODE=1
 set env DIAG_UNCALIBRATED_CLOCK=1