diff --git a/sys/bus/pci/pci_user.c b/sys/bus/pci/pci_user.c
--- a/sys/bus/pci/pci_user.c
+++ b/sys/bus/pci/pci_user.c
@@ -314,6 +314,7 @@
 	int error, ionum, i, num_patterns;
 #ifdef PRE7_COMPAT
 	struct pci_conf_old conf_old;
+	memset(&conf_old, 0, sizeof(conf_old));
 	struct pci_io iodata;
 	struct pci_io_old *io_old;
 	struct pci_match_conf_old *pattern_buf_old;