diff --git a/clutter/clutter-backend.c b/clutter/clutter-backend.c
index 8451e1d9b..064e9fee4 100644
--- a/clutter/clutter-backend.c
+++ b/clutter/clutter-backend.c
@@ -321,11 +321,14 @@ clutter_backend_set_resolution (ClutterBackend *backend,
                                 gdouble         dpi)
 {
   ClutterFixed fixed_dpi;
+  ClutterBackendPrivate *priv;
 
   g_return_if_fail (CLUTTER_IS_BACKEND (backend));
 
   if (dpi < 0)
-    dpi = -1.0
+    dpi = -1.0;
+
+  priv = backend->priv;
 
   fixed_dpi = CLUTTER_FLOAT_TO_FIXED (dpi);
   if (priv->resolution != fixed_dpi)
diff --git a/clutter/glx/clutter-backend-glx.c b/clutter/glx/clutter-backend-glx.c
index 25e9d313c..b3f4a4d21 100644
--- a/clutter/glx/clutter-backend-glx.c
+++ b/clutter/glx/clutter-backend-glx.c
@@ -205,8 +205,8 @@ clutter_backend_glx_post_parse (ClutterBackend  *backend,
 	}
 #endif
       
-      dpi = (((double) DisplayHeight (xdisplay, xscreen) * 25.4)
-            / (double) DisplayHeightMM (xdisplay, xscreen));
+      dpi = (((double) DisplayHeight (backend_glx->xdpy, backend_glx->xscreen_num) * 25.4)
+            / (double) DisplayHeightMM (backend_glx->xdpy, backend_glx->xscreen_num));
 
       clutter_backend_set_resolution (backend, dpi);