diff --git a/src/backends/x11/meta-monitor-manager-xrandr.c b/src/backends/x11/meta-monitor-manager-xrandr.c
index c369d4960..600422032 100644
--- a/src/backends/x11/meta-monitor-manager-xrandr.c
+++ b/src/backends/x11/meta-monitor-manager-xrandr.c
@@ -71,6 +71,9 @@ struct _MetaMonitorManagerXrandr
 
   int max_screen_width;
   int max_screen_height;
+
+  float *supported_scales;
+  int n_supported_scales;
 };
 
 struct _MetaMonitorManagerXrandrClass
@@ -1481,6 +1484,17 @@ meta_monitor_manager_xrandr_ensure_initial_config (MetaMonitorManager *manager)
   meta_monitor_manager_update_logical_state_derived (manager, config);
 }
 
+static void
+meta_monitor_manager_xrandr_rebuild_derived (MetaMonitorManager *manager,
+                                             MetaMonitorsConfig *config)
+{
+  MetaMonitorManagerXrandr *manager_xrandr =
+    META_MONITOR_MANAGER_XRANDR (manager);
+
+  g_clear_pointer (&manager_xrandr->supported_scales, g_free);
+  meta_monitor_manager_rebuild_derived (manager, config);
+}
+
 static gboolean
 meta_monitor_manager_xrandr_apply_monitors_config (MetaMonitorManager      *manager,
                                                    MetaMonitorsConfig      *config,
@@ -1492,7 +1506,7 @@ meta_monitor_manager_xrandr_apply_monitors_config (MetaMonitorManager      *mana
 
   if (!config)
     {
-      meta_monitor_manager_rebuild_derived (manager, NULL);
+      meta_monitor_manager_xrandr_rebuild_derived (manager, NULL);
       return TRUE;
     }
 
@@ -1526,7 +1540,7 @@ meta_monitor_manager_xrandr_apply_monitors_config (MetaMonitorManager      *mana
         }
       else
         {
-          meta_monitor_manager_rebuild_derived (manager, config);
+          meta_monitor_manager_xrandr_rebuild_derived (manager, config);
         }
     }
 
@@ -1782,6 +1796,76 @@ meta_monitor_manager_xrandr_calculate_monitor_mode_scale (MetaMonitorManager *ma
   return meta_monitor_calculate_mode_scale (monitor, monitor_mode);
 }
 
+static void
+add_supported_scale (GArray *supported_scales,
+                     float   scale)
+{
+  unsigned int i;
+
+  for (i = 0; i < supported_scales->len; i++)
+    {
+      float supported_scale = g_array_index (supported_scales, float, i);
+
+      if (scale == supported_scale)
+        return;
+    }
+
+  g_array_append_val (supported_scales, scale);
+}
+
+static int
+compare_scales (gconstpointer a,
+                gconstpointer b)
+{
+  float f = *(float *) a - *(float *) b;
+
+  if (f < 0)
+    return -1;
+  if (f > 0)
+    return 1;
+  return 0;
+}
+
+static void
+ensure_supported_monitor_scales (MetaMonitorManager *manager)
+{
+  MetaMonitorManagerXrandr *manager_xrandr =
+    META_MONITOR_MANAGER_XRANDR (manager);
+  MetaMonitorScalesConstraint constraints;
+  GList *l;
+  GArray *supported_scales;
+
+  if (manager_xrandr->supported_scales)
+    return;
+
+  constraints = META_MONITOR_SCALES_CONSTRAINT_NO_FRAC;
+  supported_scales = g_array_new (FALSE, FALSE, sizeof (float));
+
+  for (l = manager->monitors; l; l = l->next)
+    {
+      MetaMonitor *monitor = l->data;
+      MetaMonitorMode *monitor_mode;
+      float *monitor_scales;
+      int n_monitor_scales;
+      int i;
+
+      monitor_mode = meta_monitor_get_preferred_mode (monitor);
+      monitor_scales =
+        meta_monitor_calculate_supported_scales (monitor,
+                                                 monitor_mode,
+                                                 constraints,
+                                                 &n_monitor_scales);
+
+      for (i = 0; i < n_monitor_scales; i++)
+        add_supported_scale (supported_scales, monitor_scales[i]);
+      g_array_sort (supported_scales, compare_scales);
+    }
+
+  manager_xrandr->supported_scales = (float *) supported_scales->data;
+  manager_xrandr->n_supported_scales = supported_scales->len;
+  g_array_free (supported_scales, FALSE);
+}
+
 static float *
 meta_monitor_manager_xrandr_calculate_supported_scales (MetaMonitorManager          *manager,
                                                         MetaLogicalMonitorLayoutMode layout_mode,
@@ -1789,12 +1873,14 @@ meta_monitor_manager_xrandr_calculate_supported_scales (MetaMonitorManager
                                                         MetaMonitorMode             *monitor_mode,
                                                         int                         *n_supported_scales)
 {
-  MetaMonitorScalesConstraint constraints;
+  MetaMonitorManagerXrandr *manager_xrandr =
+    META_MONITOR_MANAGER_XRANDR (manager);
 
-  constraints = META_MONITOR_SCALES_CONSTRAINT_NO_FRAC;
-  return meta_monitor_calculate_supported_scales (monitor, monitor_mode,
-                                                  constraints,
-                                                  n_supported_scales);
+  ensure_supported_monitor_scales (manager);
+
+  *n_supported_scales = manager_xrandr->n_supported_scales;
+  return g_memdup (manager_xrandr->supported_scales,
+                   manager_xrandr->n_supported_scales * sizeof (float));
 }
 
 static MetaMonitorManagerCapability
@@ -1874,6 +1960,7 @@ meta_monitor_manager_xrandr_finalize (GObject *object)
   manager_xrandr->resources = NULL;
 
   g_hash_table_destroy (manager_xrandr->tiled_monitor_atoms);
+  g_free (manager_xrandr->supported_scales);
 
   G_OBJECT_CLASS (meta_monitor_manager_xrandr_parent_class)->finalize (object);
 }
@@ -1949,7 +2036,7 @@ meta_monitor_manager_xrandr_handle_xevent (MetaMonitorManagerXrandr *manager_xra
           config = NULL;
         }
 
-      meta_monitor_manager_rebuild_derived (manager, config);
+      meta_monitor_manager_xrandr_rebuild_derived (manager, config);
     }
 
   return TRUE;