diff --git a/gdk/quartz/gdkscreen-quartz.c b/gdk/quartz/gdkscreen-quartz.c
index e6f0c44e7..3daad2d6e 100644
--- a/gdk/quartz/gdkscreen-quartz.c
+++ b/gdk/quartz/gdkscreen-quartz.c
@@ -83,13 +83,16 @@ _gdk_screen_quartz_init (GdkScreenQuartz *screen_quartz)
 {
   GdkScreen *screen = GDK_SCREEN (screen_quartz);
   NSScreen *nsscreen;
+  NSDictionary *dd;
+  NSSize size;
 
   gdk_screen_set_default_colormap (screen,
                                    gdk_screen_get_system_colormap (screen));
 
   nsscreen = [[NSScreen screens] objectAtIndex:0];
-  gdk_screen_set_resolution (screen,
-                             72.0 * [nsscreen userSpaceScaleFactor]);
+  dd = [nsscreen deviceDescription];
+  size = [[dd valueForKey:NSDeviceResolution] sizeValue];
+  gdk_screen_set_resolution (screen, size.width / [nsscreen backingScaleFactor]);
 
   gdk_screen_quartz_calculate_layout (screen_quartz);
 
@@ -357,17 +360,12 @@ gdk_screen_get_height (GdkScreen *screen)
 static gint
 get_mm_from_pixels (NSScreen *screen, int pixels)
 {
-  /* userSpaceScaleFactor is in "pixels per point", 
-   * 72 is the number of points per inch, 
-   * and 25.4 is the number of millimeters per inch.
-   */
-#if MAC_OS_X_VERSION_MAX_ALLOWED > MAC_OS_X_VERSION_10_3
-  float dpi = [screen userSpaceScaleFactor] * 72.0;
-#else
-  float dpi = 96.0 / 72.0;
-#endif
-
-  return (pixels / dpi) * 25.4;
+  const float mm_per_inch = 25.4;
+  NSScreen *nsscreen = [[NSScreen screens] objectAtIndex:0];
+  NSDictionary *dd = [nsscreen deviceDescription];
+  NSSize size = [[dd valueForKey:NSDeviceResolution] sizeValue];
+  float dpi = size.width / [nsscreen backingScaleFactor];
+  return (pixels / dpi) * mm_per_inch;
 }
 
 static NSScreen *