diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6c3f4d927d..ed87dc30a2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -254,6 +254,10 @@ if(CMAKE_COMPILER_IS_GNUCXX AND CMAKE_SYSTEM_NAME STREQUAL "Linux")
   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--no-undefined")
   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--no-undefined")
   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -Wl,--no-undefined")
+
+  # For O_CLOEXEC, O_DIRECTORY, and O_NOFOLLOW flags on older systems
+  # (pre POSIX.1-2008: glibc 2.11 and earlier). #4042
+  add_definitions(-D_GNU_SOURCE)
 endif()
 
 if(CMAKE_COMPILER_IS_GNUCXX AND CMAKE_SYSTEM_NAME STREQUAL "SunOS")