diff --git a/regress/tty-margins-sb.sh b/regress/tty-margins-sb.sh
index e0840fbc3..6f573af92 100755
--- a/regress/tty-margins-sb.sh
+++ b/regress/tty-margins-sb.sh
@@ -38,10 +38,10 @@ print "\r\nNEWROW";
 sleep 100;
 PERL
 
-i=0
+j=0
 for margins in on off; do
-	INNER="$TEST_TMUX -LA$i$ -f/dev/null"
-	OUTER="$TEST_TMUX -LB$i$ -f/dev/null"
+	INNER="$TEST_TMUX -LA$j$$ -f/dev/null"
+	OUTER="$TEST_TMUX -LB$j$$ -f/dev/null"
 
 	$INNER new-session -d -s inner -x 40 -y 6 \
 	    "TRIGGER='$DIR/trigger-$margins' perl '$DIR/emitter.pl'" || exit 1
@@ -90,7 +90,7 @@ for margins in on off; do
 	    fail "$margins: terminal did not contain the expected scrolled rows"
 	$OUTER kill-server 2>/dev/null
 	$INNER kill-server 2>/dev/null
-	i=$((i + 1))
+	j=$((j + 1))
 done
 
 exit 0