diff --git a/smug.go b/smug.go
index f0589fc..821124c 100644
--- a/smug.go
+++ b/smug.go
@@ -1,7 +1,6 @@
 package main
 
 import (
-	"fmt"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -138,18 +137,20 @@ func (smug Smug) Start(config Config, options Options, context Context) error {
 			return err
 		}
 
-		for pIndex, p := range w.Panes {
+		var lastPane string
+		for _, p := range w.Panes {
 			paneRoot := ExpandPath(p.Root)
 			if paneRoot == "" || !filepath.IsAbs(p.Root) {
 				paneRoot = filepath.Join(windowRoot, p.Root)
 			}
 
-			target := fmt.Sprintf("%s.%d", window, pIndex)
-			newPane, err := smug.tmux.SplitWindow(target, p.Type, paneRoot)
+			newPane, err := smug.tmux.SplitWindow(window+"."+lastPane, p.Type, paneRoot)
 			if err != nil {
 				return err
 			}
 
+			lastPane = newPane
+
 			for _, c := range p.Commands {
 				err = smug.tmux.SendKeys(window+"."+newPane, c)
 				if err != nil {
diff --git a/smug_test.go b/smug_test.go
index f52408d..32dc3f9 100644
--- a/smug_test.go
+++ b/smug_test.go
@@ -79,7 +79,7 @@ var testTable = []struct {
 			"tmux new -Pd -s ses -n smug_def -c root",
 			"tmux neww -Pd -t ses: -n win1 -c root",
 			"tmux select-layout -t ses:win1 main-horizontal",
-			"tmux split-window -Pd -h -t ses:win1.0 -c root -F #{pane_id}",
+			"tmux split-window -Pd -h -t ses:win1. -c root -F #{pane_id}",
 			"tmux kill-window -t ses:smug_def",
 			"tmux move-window -r -s ses: -t ses:",
 			"tmux attach -d -t ses:win1",
@@ -192,7 +192,7 @@ var testTable = []struct {
 			"tmux new -Pd -s ses -n smug_def -c root",
 			"tmux neww -Pd -t ses: -n win1 -c root/win1",
 			"tmux select-layout -t ses:win1 even-horizontal",
-			"tmux split-window -Pd -v -t ses:win1.0 -c root/win1/pane1 -F #{pane_id}",
+			"tmux split-window -Pd -v -t ses:win1. -c root/win1/pane1 -F #{pane_id}",
 			"tmux send-keys -t ses:win1.1 command1 Enter",
 			"tmux kill-window -t ses:smug_def",
 			"tmux move-window -r -s ses: -t ses:",