diff --git a/tmp/lanelet2_extension/test/src/test_regulatory_elements.cpp b/tmp/lanelet2_extension/test/src/test_regulatory_elements.cpp
index 7037e951..2a3285fa 100644
--- a/tmp/lanelet2_extension/test/src/test_regulatory_elements.cpp
+++ b/tmp/lanelet2_extension/test/src/test_regulatory_elements.cpp
@@ -20,6 +20,7 @@
 #include <lanelet2_core/Attribute.h>
 #include <lanelet2_core/LaneletMap.h>
 
+#include <boost/optional/optional_io.hpp>
 #include <cmath>
 #include <vector>