diff --git a/src/acpi/acpigen.c b/src/acpi/acpigen.c
index e2fe2cfaa4..7b7258469f 100644
--- a/src/acpi/acpigen.c
+++ b/src/acpi/acpigen.c
@@ -408,7 +408,7 @@ void acpigen_write_processor_cnot(const unsigned int number_of_cores)
  * len is region length.
  * OperationRegion(regionname, regionspace, regionoffset, regionlength)
  */
-void acpigen_write_opregion(struct opregion *opreg)
+void acpigen_write_opregion(const struct opregion *opreg)
 {
 	/* OpregionOp */
 	acpigen_emit_ext_op(OPREGION_OP);
diff --git a/src/include/acpi/acpigen.h b/src/include/acpi/acpigen.h
index e0d95cdbfe..d06d20c8e7 100644
--- a/src/include/acpi/acpigen.h
+++ b/src/include/acpi/acpigen.h
@@ -429,7 +429,7 @@ void acpigen_write_rom(void *bios, const size_t length);
  * This function takes input region name, region space, region offset & region
  * length.
  */
-void acpigen_write_opregion(struct opregion *opreg);
+void acpigen_write_opregion(const struct opregion *opreg);
 /*
  * Generate ACPI AML code for Mutex
  * This function takes mutex name and initial value.