diff --git a/configure.ac b/configure.ac
index 6fd50fdb..45128eaf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -135,7 +135,9 @@ dnl Checks
 AC_PROG_CC_C99
 AM_PROG_AS
 AC_USE_SYSTEM_EXTENSIONS
-CPPFLAGS="$CPPFLAGS -D_FORTIFY_SOURCE=2"
+
+AX_CHECK_COMPILE_FLAG([-D_FORTIFY_SOURCE=2],
+  [CPPFLAGS="$CPPFLAGS -D_FORTIFY_SOURCE=2"])
 
 AX_CHECK_COMPILE_FLAG([-fvisibility=hidden],
   [CFLAGS="$CFLAGS -fvisibility=hidden"])