diff --git a/src/northbridge/intel/x4x/Kconfig b/src/northbridge/intel/x4x/Kconfig
index bdef6f2..32e85d3 100644
--- a/src/northbridge/intel/x4x/Kconfig
+++ b/src/northbridge/intel/x4x/Kconfig
@@ -25,6 +25,10 @@
 config MMCONF_BASE_ADDRESS
 	default 0xe0000000
 
+config MMCONF_BUS_NUMBER
+	int
+	default 256
+
 config SMM_RESERVED_SIZE
 	hex
 	default 0x100000