diff --git a/src/ipa/raspberrypi/controller/pwl.h b/src/ipa/raspberrypi/controller/pwl.h
index 546482cd..691c4700 100644
--- a/src/ipa/raspberrypi/controller/pwl.h
+++ b/src/ipa/raspberrypi/controller/pwl.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <math.h>
+#include <functional>
 #include <vector>
 
 #include "libcamera/internal/yaml_parser.h"