diff --git a/CMakeLists.txt b/CMakeLists.txt
index 68dafa7..44f2f18 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -51,11 +51,13 @@ if (HAVE_STRERROR_R)
     test_strerror_r(HAVE_GNU_STRERROR_R)
 endif()
 if (NOT WIN32)
+    set(TMP "${CMAKE_REQUIRED_DEFINITIONS}")
     set(CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
     check_symbol_exists(fcloseall "stdio.h" HAVE_FCLOSEALL)
     if (HAVE_FCLOSEALL)
         add_compile_definitions(_GNU_SOURCE)
     endif()
+    set(CMAKE_REQUIRED_DEFINITIONS "${TMP}")
 endif()
 configure_file("${CMAKE_CURRENT_SOURCE_DIR}/utils_config.h.in" "${CMAKE_CURRENT_BINARY_DIR}/utils_config.h")