diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 37c1bbe..ffc2e4b 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -3,7 +3,7 @@ set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_CURRENT_SOURCE_DIR}/cmake/")
 set(PARSE_CATCH_TESTS_ADD_TO_CONFIGURE_DEPENDS ON)
 include(ParseAndAddCatchTests)
 
-if(NOT DEFINED ENV{GHC_COVERAGE})
+if(NOT ENV{GHC_COVERAGE})
     add_executable(filesystem_test filesystem_test.cpp catch.hpp)
     target_link_libraries(filesystem_test ghc_filesystem)
     target_compile_options(filesystem_test PRIVATE