diff --git a/lisp/face-remap.el b/lisp/face-remap.el
index c899a8d..53e99ec 100644
--- a/lisp/face-remap.el
+++ b/lisp/face-remap.el
@@ -203,6 +203,19 @@ Each positive or negative step scales the default face height by this amount."
 (defvar text-scale-mode-amount 0)
 (make-variable-buffer-local 'text-scale-mode-amount)
 
+(defvar text-scale-mode-old-scale-factor nil
+  "Previously active scale factor for default face :height
+attribute when `text-scale-mode-hook' is called, or nil if
+text-scale-mode was not previously active (meaning the old scale
+factor was 1.0).")
+(make-variable-buffer-local 'text-scale-mode-old-scale-factor)
+
+(defvar text-scale-mode-scale-factor nil
+  "Scale factor for default face :height attribute when
+`text-scale-mode-hook' is called, or nil if text-scale-mode will
+be deactivated (meaning the scale factor is 1.0).")
+(make-variable-buffer-local 'text-scale-mode-scale-factor)
+
 (define-minor-mode text-scale-mode
   "Minor mode for displaying buffer text in a larger/smaller font than usual.
 
@@ -221,14 +234,55 @@ disable `text-scale-mode' as necessary)."
   (setq text-scale-mode-lighter
 	(format (if (>= text-scale-mode-amount 0) "+%d" "%d")
 		text-scale-mode-amount))
+  (setq text-scale-mode-old-scale-factor
+	(nth 2 text-scale-mode-remapping))
+  (setq text-scale-mode-scale-factor
+	(and text-scale-mode
+	     (expt text-scale-mode-step text-scale-mode-amount)))
   (setq text-scale-mode-remapping
 	(and text-scale-mode
 	     (face-remap-add-relative 'default
-					  :height
-					  (expt text-scale-mode-step
-						text-scale-mode-amount))))
+				      :height text-scale-mode-scale-factor)))
   (force-window-update (current-buffer)))
 
+(defun text-scale-mode-adjust-window-horizontal-size ()
+  "Change the horizontal size of the current window corresponding to ratio
+`text-scale-mode-scale-factor / text-scale-mode-old-scale-factor'.
+
+This function is intended to be used as a hook for `text-scale-mode-hook'."
+  (let* ((edges (window-edges))
+	 (owidth (- (nth 2 edges) (nth 0 edges)))
+	 (scale-factor
+	  (/ (or text-scale-mode-scale-factor 1.0)
+	     (or text-scale-mode-old-scale-factor 1.0))))
+    (condition-case nil
+	(enlarge-window-horizontally
+	 (round (- (* owidth scale-factor) owidth)))
+      (error nil))))
+
+(defun text-scale-mode-adjust-window-vertical-size ()
+  "Change the vertical size of the current window corresponding to ratio
+`text-scale-mode-scale-factor / text-scale-mode-old-scale-factor'.
+
+This function is intended to be used as a hook for `text-scale-mode-hook'."
+  (let* ((edges (window-edges))
+	 (oheight (- (nth 3 edges) (nth 1 edges)))
+	 (scale-factor
+	  (/ (or text-scale-mode-scale-factor 1.0)
+	     (or text-scale-mode-old-scale-factor 1.0))))
+    (condition-case nil
+	(enlarge-window
+	 (round (- (* oheight scale-factor) oheight)))
+      (error nil))))
+
+(defun text-scale-mode-adjust-window-size ()
+  "Change the size of the current window corresponding to ratio
+`text-scale-mode-scale-factor / text-scale-mode-old-scale-factor'.
+
+This function is intended to be used as a hook for `text-scale-mode-hook'."
+  (text-scale-mode-adjust-window-vertical-size)
+  (text-scale-mode-adjust-window-horizontal-size))
+
 ;;;###autoload
 (defun text-scale-set (level)
   "Set the scale factor of the default face in the current buffer to LEVEL.