diff --git a/src/device/pciexp_device.c b/src/device/pciexp_device.c
index 5e2709e38a..e0b3544874 100644
--- a/src/device/pciexp_device.c
+++ b/src/device/pciexp_device.c
@@ -8,7 +8,7 @@
 #include <device/pci_ops.h>
 #include <device/pciexp.h>
 
-unsigned int pciexp_find_extended_cap(struct device *dev, unsigned int cap)
+unsigned int pciexp_find_extended_cap(const struct device *dev, unsigned int cap)
 {
 	unsigned int this_cap_offset, next_cap_offset;
 	unsigned int this_cap, cafe;
diff --git a/src/include/device/pciexp.h b/src/include/device/pciexp.h
index 756733e0d8..a72c2ec2a9 100644
--- a/src/include/device/pciexp.h
+++ b/src/include/device/pciexp.h
@@ -30,7 +30,7 @@ void pciexp_hotplug_scan_bridge(struct device *dev);
 
 extern struct device_operations default_pciexp_hotplug_ops_bus;
 
-unsigned int pciexp_find_extended_cap(struct device *dev, unsigned int cap);
+unsigned int pciexp_find_extended_cap(const struct device *dev, unsigned int cap);
 
 static inline bool pciexp_is_downstream_port(int type)
 {