diff --git a/tests/modules/testFluka.cpp b/tests/modules/testFluka.cpp
index 2b379fc69c6f8c128364886c9e11f6ff0e234ee7..acd24b30813668b25684f06643d7e81885a129ae 100644
--- a/tests/modules/testFluka.cpp
+++ b/tests/modules/testFluka.cpp
@@ -27,6 +27,7 @@
 #include <SetupTestEnvironment.hpp>
 
 using namespace corsika;
+using Catch::Approx;
 
 template <typename TStackView>
 auto sumMomentum(TStackView const& view, CoordinateSystemPtr const& vCS) {