diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index ab12e064aaa..0b0192a545d 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2014-11-08  Glenn Morris  <rgm@gnu.org>
+
+	* emacs-lisp/bytecomp.el (byte-compile-report-error):
+	Allow the argument to be a string.  Due to the vague doc,
+	it was already being used this way.
+
 2014-11-08  Michael Albinus  <michael.albinus@gmx.de>
 
 	* net/tramp.el (tramp-check-cached-permissions): Include hop in
diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index 7fd72dd7705..fdb8cc8f39d 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -1165,10 +1165,13 @@ Each function's symbol gets added to `byte-compile-noruntime-functions'."
 	(byte-compile-warn "%s" msg)))))
 
 (defun byte-compile-report-error (error-info)
-  "Report Lisp error in compilation.  ERROR-INFO is the error data."
+  "Report Lisp error in compilation.
+ERROR-INFO is the error data, in the form of either (ERROR-SYMBOL . DATA)
+or STRING."
   (setq byte-compiler-error-flag t)
   (byte-compile-log-warning
-   (error-message-string error-info)
+   (if (stringp error-info) error-info
+     (error-message-string error-info))
    nil :error))
 
 ;;; sanity-checking arglists
diff --git a/src/ChangeLog b/src/ChangeLog
index e3f34e27dfc..82a9b24876c 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -2,6 +2,8 @@
 
 	* nsterm.m (run): Only use non-system event loop if OSX version is
 	exactly 10.9 (Bug#18993).
+	(ns_set_vertical_scroll_bar): Don't call bar setPosition: unless
+	needed (Bug#18757).
 
 2014-11-08  Michael Albinus  <michael.albinus@gmx.de>
 
diff --git a/src/nsterm.m b/src/nsterm.m
index 216678357e7..318f14acfc8 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -3759,6 +3759,7 @@ overwriting cursor (usually when cursor on a tab) */
   EmacsScroller *bar;
   int window_y, window_height;
   int top, left, height, width;
+  BOOL update_p = YES;
 
   /* optimization; display engine sends WAY too many of these.. */
   if (!NILP (window->vertical_scroll_bar))
@@ -3773,6 +3774,7 @@ overwriting cursor (usually when cursor on a tab) */
             }
           else
             view->scrollbarsNeedingUpdate--;
+          update_p = NO;
         }
     }
 
@@ -3814,6 +3816,7 @@ overwriting cursor (usually when cursor on a tab) */
 
       bar = [[EmacsScroller alloc] initFrame: r window: win];
       wset_vertical_scroll_bar (window, make_save_ptr (bar));
+      update_p = YES;
     }
   else
     {
@@ -3916,10 +3919,12 @@ overwriting cursor (usually when cursor on a tab) */
           if (oldRect.origin.x != r.origin.x)
               ns_clear_frame_area (f, left, top, width, height);
           [bar setFrame: r];
+          update_p = YES;
         }
     }
 
-  [bar setPosition: position portion: portion whole: whole];
+  if (update_p)
+    [bar setPosition: position portion: portion whole: whole];
   unblock_input ();
 }