diff --git a/src/xfce-desktop.c b/src/xfce-desktop.c
index 40d74037..bb108343 100644
--- a/src/xfce-desktop.c
+++ b/src/xfce-desktop.c
@@ -93,6 +93,7 @@ struct _XfceDesktopPrivate
     GdkScreen *gscreen;
     WnckScreen *wnck_screen;
     gboolean updates_frozen;
+    guint primary_monitor;
 
     XfconfChannel *channel;
     gchar *property_prefix;
@@ -689,10 +690,21 @@ xfce_desktop_monitors_changed(GdkScreen *gscreen,
 
     TRACE("entering");
 
+    desktop->priv->primary_monitor = 0;
+
+    /* Update the primary monitor number */
+    for(i = 0; i < xfce_desktop_get_n_monitors(desktop); i++) {
+        if(gdk_monitor_is_primary(gdk_display_get_monitor(gdk_screen_get_display(gscreen), i))) {
+            desktop->priv->primary_monitor = i;
+            break;
+        }
+    }
+
     /* Update the workspaces */
     for(i = 0; i < desktop->priv->nworkspaces; i++) {
         xfce_workspace_monitors_changed(desktop->priv->workspaces[i],
-                                        gscreen);
+                                        gscreen,
+                                        desktop->priv->primary_monitor);
     }
 
     /* fake a screen size changed, so the background is properly set */
@@ -725,7 +737,7 @@ workspace_backdrop_changed_cb(XfceWorkspace *workspace,
         /* Update the backdrop!
          * In spanning mode, ignore updates to monitors other than the primary
          */
-        if(!xfce_workspace_get_xinerama_stretch(workspace) || monitor == 0) {
+        if(!xfce_workspace_get_xinerama_stretch(workspace) || monitor == desktop->priv->primary_monitor) {
             backdrop_changed_cb(backdrop, user_data);
         }
     }
@@ -789,7 +801,8 @@ workspace_created_cb(WnckScreen *wnck_screen,
                                                                     nlast_workspace);
 
     xfce_workspace_monitors_changed(desktop->priv->workspaces[nlast_workspace],
-                                    desktop->priv->gscreen);
+                                    desktop->priv->gscreen,
+                                    0);
 
     g_signal_connect(desktop->priv->workspaces[nlast_workspace],
                      "workspace-backdrop-changed",
diff --git a/src/xfce-workspace.c b/src/xfce-workspace.c
index 69b972f6..9ad18eea 100644
--- a/src/xfce-workspace.c
+++ b/src/xfce-workspace.c
@@ -76,6 +76,7 @@
 struct _XfceWorkspacePrivate
 {
     GdkScreen *gscreen;
+    guint primary;
 
     XfconfChannel *channel;
     gchar *property_prefix;
@@ -123,17 +124,17 @@ G_DEFINE_TYPE_WITH_PRIVATE(XfceWorkspace, xfce_workspace, G_TYPE_OBJECT)
  * xfce_workspace_get_xinerama_stretch:
  * @workspace: An #XfceWorkspace.
  *
- * returns whether the first backdrop is set to spanning screens since it's
- * the only backdrop where that setting is applicable.
+ * returns whether the backdrop of the primary monitor is set to spanning screens
+ * since it's the only backdrop where that setting is applicable.
  **/
 gboolean
 xfce_workspace_get_xinerama_stretch(XfceWorkspace *workspace)
 {
     g_return_val_if_fail(XFCE_IS_WORKSPACE(workspace), FALSE);
     g_return_val_if_fail(workspace->priv->backdrops != NULL, FALSE);
-    g_return_val_if_fail(XFCE_IS_BACKDROP(workspace->priv->backdrops[0]), FALSE);
+    g_return_val_if_fail(XFCE_IS_BACKDROP(workspace->priv->backdrops[workspace->priv->primary]), FALSE);
 
-    return xfce_backdrop_get_image_style(workspace->priv->backdrops[0]) == XFCE_BACKDROP_IMAGE_SPANNING_SCREENS;
+    return xfce_backdrop_get_image_style(workspace->priv->backdrops[workspace->priv->primary]) == XFCE_BACKDROP_IMAGE_SPANNING_SCREENS;
 }
 
 static void
@@ -282,13 +283,15 @@ backdrop_changed_cb(XfceBackdrop *backdrop, gpointer user_data)
 /**
  * xfce_workspace_monitors_changed:
  * @workspace: An #XfceWorkspace.
- * @GdkScreen: screen the workspace is on.
+ * @gscreen: screen the workspace is on.
+ * @primary: primary monitor number
  *
  * Updates the backdrops to correctly display the right settings.
  **/
 void
 xfce_workspace_monitors_changed(XfceWorkspace *workspace,
-                                GdkScreen *gscreen)
+                                GdkScreen *gscreen,
+                                guint primary)
 {
     guint i;
     guint n_monitors;
@@ -298,6 +301,9 @@ xfce_workspace_monitors_changed(XfceWorkspace *workspace,
 
     g_return_if_fail(gscreen);
 
+    /* Set primary monitor number */
+    workspace->priv->primary = primary;
+
     vis = gdk_screen_get_rgba_visual(gscreen);
     if(vis == NULL)
         vis = gdk_screen_get_system_visual(gscreen);
@@ -749,6 +755,7 @@ xfce_workspace_new(GdkScreen *gscreen,
         gscreen = gdk_display_get_default_screen(gdk_display_get_default());
 
     workspace->priv->gscreen = gscreen;
+    workspace->priv->primary = 0;
     workspace->priv->workspace_num = number;
     workspace->priv->channel = XFCONF_CHANNEL(g_object_ref(G_OBJECT(channel)));
     workspace->priv->property_prefix = g_strdup(property_prefix);
diff --git a/src/xfce-workspace.h b/src/xfce-workspace.h
index aabf13e3..f9d0c4a9 100644
--- a/src/xfce-workspace.h
+++ b/src/xfce-workspace.h
@@ -66,11 +66,11 @@ gint xfce_workspace_get_workspace_num(XfceWorkspace *workspace);
 void xfce_workspace_set_workspace_num(XfceWorkspace *workspace, gint number);
 
 void xfce_workspace_monitors_changed(XfceWorkspace *workspace,
-                                     GdkScreen *gscreen);
+                                     GdkScreen *gscreen,
+                                     guint primary);
 
 gboolean xfce_workspace_get_xinerama_stretch(XfceWorkspace *workspace);
 
-
 XfceBackdrop *xfce_workspace_get_backdrop(XfceWorkspace *workspace,
                                           guint monitor);