diff --git a/Components/OPL2/Implementation/Operator.cpp b/Components/OPL2/Implementation/Operator.cpp
index 57824c9f3..b388b9838 100644
--- a/Components/OPL2/Implementation/Operator.cpp
+++ b/Components/OPL2/Implementation/Operator.cpp
@@ -9,6 +9,7 @@
 #include "Operator.hpp"
 
 #include <algorithm>
+#include <cassert>
 
 using namespace Yamaha::OPL;