diff --git a/ChangeLog b/ChangeLog
index 007b2183ee..8a1dc1fa1a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Thu Oct  9 07:20:30 2014  Rei Odaira  <Rei.Odaira@gmail.com>
+
+	* missing/setproctitle.c: Avoid invalidating argv[1], argv[2],
+	  etc. until the first call to Process.setproctitle, because
+	  the ps command of AIX refers to the argv array.
+	  [Bug #10090]
+
 Thu Oct  9 00:53:15 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* dir.c (dir_s_aref): fix rdoc.  `Dir.glob` allows an array but
diff --git a/missing/setproctitle.c b/missing/setproctitle.c
index 9dcf37560b..602ddf105c 100644
--- a/missing/setproctitle.c
+++ b/missing/setproctitle.c
@@ -74,6 +74,7 @@
 static char *argv_start = NULL;
 static size_t argv_env_len = 0;
 static size_t argv_len = 0;
+static char **argv1_addr = NULL;
 #endif
 
 #endif /* HAVE_SETPROCTITLE */
@@ -119,7 +120,9 @@ compat_init_setproctitle(int argc, char *argv[])
 			lastenvp = envp[i] + strlen(envp[i]);
 	}
 
-	argv[1] = NULL;
+	/* We keep argv[1], argv[2], etc. at this moment,
+	   because the ps command of AIX refers to them. */
+	argv1_addr = &argv[1];
 	argv_start = argv[0];
 	argv_len = lastargv - argv[0];
 	argv_env_len = lastenvp - argv[0];
@@ -162,6 +165,8 @@ setproctitle(const char *fmt, ...)
 	argvlen = len > argv_len ? argv_env_len : argv_len;
 	for(; len < argvlen; len++)
 		argv_start[len] = SPT_PADCHAR;
+	/* argv[1], argv[2], etc. are no longer valid. */
+	*argv1_addr = NULL;
 #endif
 
 #endif /* SPT_NONE */