diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index ddb7a0a..f43f1eb 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -316,7 +316,7 @@
 
 # Pick a "unique" port in the range 10000-19999.
 PORT="0000$$"
-PORT="1$(echo $PORT | tail -c 4)"
+PORT="1$(echo $PORT | tail -c 5)"
 
 # fix commands to use this port
 P_SRV="$P_SRV server_port=$PORT"