diff --git a/src/drivers/bus/isa.c b/src/drivers/bus/isa.c
index da0c43c60..6b360a44d 100644
--- a/src/drivers/bus/isa.c
+++ b/src/drivers/bus/isa.c
@@ -5,6 +5,7 @@
 #include <errno.h>
 #include <ipxe/io.h>
 #include <ipxe/isa.h>
+#include <config/isa.h>
 
 FILE_LICENCE ( GPL2_OR_LATER );