diff --git a/CMakeLists.txt b/CMakeLists.txt
index 021b08f..cf21e05 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -150,7 +150,7 @@ pkg_check_modules (POPT REQUIRED popt)
 if(${GSSAPI_VERSION} VERSION_LESS "7.5.0")
 	add_definitions(-DOLD_HEIMDAL)
 endif()
-set (CMAKE_C_FLAGS "-fPIC -O2 -D_FORTIFY_SOURCE=2 -fstack-protector ${CMAKE_C_FLAGS}")
+set (CMAKE_C_FLAGS "-fPIC -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector ${CMAKE_C_FLAGS}")
 set (CMAKE_C_FLAGS "-Wno-unused-result -fno-strict-aliasing ${CMAKE_C_FLAGS}")
 set (LINKER_HARDENING_FLAGS     "-Wl,-z,relro -Wl,-z,now")