diff --git a/ChangeLog b/ChangeLog
index fc42ede427..801ac5d40b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Aug 29 22:01:15 2012  Tanaka Akira  <akr@fsij.org>
+
+	* process.c (rb_f_system): check failures of waitpid.
+	  [ruby-talk:398687]
+
 Wed Aug 29 15:03:04 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* configure.in (LIBDIR_BASENAME): use configured libdir value to fix
diff --git a/process.c b/process.c
index fe0587119e..25eed71a4e 100644
--- a/process.c
+++ b/process.c
@@ -3661,7 +3661,10 @@ rb_f_system(int argc, VALUE *argv)
     pid = rb_spawn_internal(argc, argv, NULL, 0);
 #if defined(HAVE_FORK) || defined(HAVE_SPAWNV)
     if (pid > 0) {
-	rb_syswait(pid);
+        int ret, status;
+        ret = rb_waitpid(pid, &status, 0);
+        if (ret == (rb_pid_t)-1)
+            rb_sys_fail("Another thread waited the process started by system().");
     }
 #endif
 #ifdef SIGCHLD