diff --git a/process.c b/process.c
index 4268e33a25..14c8d1b169 100644
--- a/process.c
+++ b/process.c
@@ -1777,14 +1777,15 @@ rb_spawn(int argc, VALUE *argv)
  *     *
  */
 
-#if defined(SIGCLD) && !defined(SIGCHLD)
-# define SIGCHLD SIGCLD
-#endif
-
 static VALUE
 rb_f_system(int argc, VALUE *argv)
 {
     int status;
+
+#if defined(SIGCLD) && !defined(SIGCHLD)
+# define SIGCHLD SIGCLD
+#endif
+
 #ifdef SIGCHLD
     RETSIGTYPE (*chfunc)(int);