diff --git a/hw/xfree86/modes/xf86Crtc.c b/hw/xfree86/modes/xf86Crtc.c
index 2a02c8507..a441fd16a 100644
--- a/hw/xfree86/modes/xf86Crtc.c
+++ b/hw/xfree86/modes/xf86Crtc.c
@@ -1863,6 +1863,9 @@ SetCompatOutput(xf86CrtcConfigPtr config)
     DisplayModePtr maxmode = NULL, testmode, mode;
     int o, compat = -1, count, mincount = 0;
 
+    if (config->num_output == 0)
+        return NULL;
+
     /* Look for one that's definitely connected */
     for (o = 0; o < config->num_output; o++) {
         test = config->output[o];