diff --git a/src/device/oprom/realmode/x86.c b/src/device/oprom/realmode/x86.c
index 367614d..c3adf40 100644
--- a/src/device/oprom/realmode/x86.c
+++ b/src/device/oprom/realmode/x86.c
@@ -415,7 +415,7 @@
 
 void run_bios(struct device *dev, unsigned long addr)
 {
-	u32 num_dev = (dev->bus->secondary << 8) | dev->path.pci.devfn;
+	u32 num_dev = (dev->upstream->secondary << 8) | dev->path.pci.devfn;
 
 	/* Setting up required hardware.
 	 * Removing this will cause random illegal instruction exceptions