diff --git a/exwm-workspace.el b/exwm-workspace.el
index 1bdc724..490d83a 100644
--- a/exwm-workspace.el
+++ b/exwm-workspace.el
@@ -368,40 +368,40 @@ FRAME may be either a workspace frame or a workspace position."
             (pcase edge
               ;; Left and top are always processed first.
               (`left
-               (setq delta (- x size))
-               (when (and (< delta 0)
+               (setq delta (- size x))
+               (when (and (< 0 delta)
                           (or (not position)
                               (< (max beg y)
                                  (min end (+ y height)))))
-                 (cl-incf width delta)
+                 (cl-decf width delta)
                  (setf x size)))
               (`right
-               (setq delta (- root-width x width size))
-               (when (and (< delta 0)
+               (setq delta (- size (- root-width x width)))
+               (when (and (< 0 delta)
                           (or (not position)
                               (< (max beg y)
                                  (min end (+ y height)))))
-                 (cl-incf width delta)))
+                 (cl-decf width delta)))
               (`top
-               (setq delta (- y size))
-               (when (and (< delta 0)
+               (setq delta (- size y))
+               (when (and (< 0 delta)
                           (or (not position)
                               (< (max beg x)
                                  (min end (+ x width))))
                           (< size (+ y height))
                           (> size y))
-                 (cl-incf height delta)
+                 (cl-decf height delta)
                  (setf y size)))
               (`bottom
-               (setq delta (- root-height y height size))
-               (when (and (< delta 0)
+               (setq delta (- size (- root-height y height)))
+               (when (and (< 0 delta)
                           (or (not position)
                               (< (max beg x)
                                  (min end (+ x width))))
                           (< (- root-height size)
                              (+ y height))
                           (> (- root-height size) y))
-                 (cl-incf height delta))))))))
+                 (cl-decf height delta))))))))
     ;; Save the result.
     (setq exwm-workspace--workareas workareas)
     (xcb:flush exwm--connection))