diff --git a/source/RobotAPI/components/armem/client/ObjectInstanceToIndex/ObjectInstanceToIndex.h b/source/RobotAPI/components/armem/client/ObjectInstanceToIndex/ObjectInstanceToIndex.h
index c5e6486e7ded27538c715f1ba48531a1fd552b1f..ca3344af472d7fc3ee8b4b2e02a9134d5a05c892 100644
--- a/source/RobotAPI/components/armem/client/ObjectInstanceToIndex/ObjectInstanceToIndex.h
+++ b/source/RobotAPI/components/armem/client/ObjectInstanceToIndex/ObjectInstanceToIndex.h
@@ -22,6 +22,8 @@
 
 #pragma once
 
+#include <mutex>
+
 #include <ArmarXCore/core/Component.h>
 #include <ArmarXCore/core/time/Frequency.h>