--- a/src/lwp_ucontext.c	
+++ a/src/lwp_ucontext.c	
@@ -14,6 +14,10 @@ Coda are listed in the file CREDITS.
            Additional copyrights
 #*/
 
+/* avoid breaking longjmp stack switching */
+#undef _FORTIFY_SOURCE
+#define _FORTIFY_SOURCE 0
+
 #include <sys/types.h>
 #include <stdlib.h>
 #include <assert.h>
@@ -21,9 +25,6 @@ Coda are listed in the file CREDITS.
 #include <string.h>
 #include <unistd.h>
 
-/* avoid breaking longjmp stack switching */
-#undef _FORTIFY_SOURCE
-#define _FORTIFY_SOURCE 0
 #include "lwp_ucontext.h"
 
 /* Some architectures have a stack that grows up instead of down */