diff --git a/regress/session-group-name.sh b/regress/session-group-name.sh
new file mode 100644
index 000000000..979c04dd5
--- /dev/null
+++ b/regress/session-group-name.sh
@@ -0,0 +1,43 @@
+#!/bin/sh
+
+# Reusing a session name must not reuse an unrelated session group.
+
+PATH=/bin:/usr/bin
+TERM=screen
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+trap '$TMUX kill-server 2>/dev/null' 0 1 15
+
+$TMUX new -d -s a || exit 1
+$TMUX new -d -t a -s b || exit 1
+$TMUX kill-session -t a || exit 1
+
+# Occupy the first suffix too, without creating a session of that name.
+$TMUX new -d -t a-1 -s other || exit 1
+$TMUX new -d -s a || exit 1
+AW=$($TMUX display -p -t a: '#{window_id}')
+BW=$($TMUX display -p -t b: '#{window_id}')
+$TMUX new -d -t a -s c || exit 1
+
+[ "$($TMUX display -p -t a: '#{session_group}')" = a-2 ] || exit 1
+[ "$($TMUX display -p -t c: '#{session_group}')" = a-2 ] || exit 1
+[ "$($TMUX display -p -t b: '#{session_group_list}')" = b ] || exit 1
+[ "$($TMUX display -p -t a: '#{window_id}')" = "$AW" ] || exit 1
+[ "$($TMUX display -p -t c: '#{window_id}')" = "$AW" ] || exit 1
+[ "$AW" != "$BW" ] || exit 1
+
+# Window changes propagate only within the new group.
+$TMUX new-window -d -t a || exit 1
+[ "$($TMUX display -p -t c: '#{session_windows}')" = 2 ] || exit 1
+[ "$($TMUX display -p -t b: '#{session_windows}')" = 1 ] || exit 1
+
+# An existing session still joins its group; a group-only target still works.
+$TMUX new -d -t c -s d || exit 1
+[ "$($TMUX display -p -t d: '#{session_group}')" = a-2 ] || exit 1
+$TMUX new -d -t a-1 -s e || exit 1
+[ "$($TMUX display -p -t e: '#{session_group}')" = a-1 ] || exit 1
+[ "$($TMUX display -p -t e: '#{window_id}')" = \
+    "$($TMUX display -p -t other: '#{window_id}')" ] || exit 1
+
+exit 0