diff --git a/src/pane.coffee b/src/pane.coffee
index 2c1bdfd67..4375ce588 100644
--- a/src/pane.coffee
+++ b/src/pane.coffee
@@ -1,4 +1,4 @@
-{find, compact, extend} = require 'underscore-plus'
+{find, compact, extend, last} = require 'underscore-plus'
 {dirname} = require 'path'
 {Model, Sequence} = require 'theorist'
 Serializable = require 'serializable'
@@ -332,3 +332,19 @@ class Pane extends Model
 
     newPane.activate()
     newPane
+
+  # Private: If the parent is a horizontal axis, returns its first child;
+  # otherwise this pane.
+  findLeftmostSibling: ->
+    if @parent.orientation is 'horizontal'
+      @parent.children[0]
+    else
+      this
+
+  # Private: If the parent is a horizontal axis, returns its last child;
+  # otherwise returns a new pane created by splitting this pane rightward.
+  findOrCreateRightmostSibling: ->
+    if @parent.orientation is 'horizontal'
+      last(@parent.children)
+    else
+      @splitRight()
diff --git a/src/workspace.coffee b/src/workspace.coffee
index 73f2916d9..32d1657f4 100644
--- a/src/workspace.coffee
+++ b/src/workspace.coffee
@@ -115,15 +115,22 @@ class Workspace extends Model
   openSingletonSync: (uri, {changeFocus, initialLine, split}={}) ->
     changeFocus ?= true
     uri = atom.project.relativize(uri)
-    pane = @paneContainer.paneForUri(uri)
 
-    if pane
-      paneItem = pane.itemForUri(uri)
-      pane.activateItem(paneItem)
-      pane.activate() if changeFocus
-      paneItem
+    if pane = @paneContainer.paneForUri(uri)
+      editor = pane.itemForUri(uri)
     else
-      @openSync(uri, {changeFocus, initialLine, split})
+      pane = switch split
+        when 'left'
+          @activePane.findLeftmostSibling()
+        when 'right'
+          @activePane.findOrCreateRightmostSibling()
+        else
+          @activePane
+      editor = atom.project.openSync(uri, {initialLine})
+
+    pane.activateItem(editor)
+    pane.activate() if changeFocus
+    editor
 
   # Public: Reopens the last-closed item uri if it hasn't already been reopened.
   reopenItemSync: ->