diff --git a/src/ipa/raspberrypi/controller/rpi/contrast.cpp b/src/ipa/raspberrypi/controller/rpi/contrast.cpp
index 6726b4e3..be61353a 100644
--- a/src/ipa/raspberrypi/controller/rpi/contrast.cpp
+++ b/src/ipa/raspberrypi/controller/rpi/contrast.cpp
@@ -83,6 +83,7 @@ void Contrast::Initialise()
 {
 	// Fill in some default values as Prepare will run before Process gets
 	// called.
+	MutexLocker locker(mutex_);
 	fill_in_status(status_, brightness_, contrast_, config_.gamma_curve);
 }