--- a/hw/xfree86/common/xf86platformBus.c	
+++ a/hw/xfree86/common/xf86platformBus.c	
@@ -289,7 +289,7 @@ xf86platformProbe(void)
     for (i = 0; i < xf86_num_platform_devices; i++) {
         char *busid = xf86_platform_odev_attributes(i)->busid;
 
-        if (pci && (strncmp(busid, "pci:", 4) == 0)) {
+        if (pci && busid && (strncmp(busid, "pci:", 4) == 0)) {
             platform_find_pci_info(&xf86_platform_devices[i], busid);
         }