diff --git a/ChangeLog b/ChangeLog
index 591b278223..0c7f654e9e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jun 20 11:33:04 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* process.c (rb_execarg_addopt): always make Fixnum, and ignore higher
+	  bits in too large umask value.
+
 Wed Jun 20 11:24:35 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/test/unit.rb (Test::Unit::Runner#_run_parallel): deal with
diff --git a/process.c b/process.c
index 326f379661..6f230ee61b 100644
--- a/process.c
+++ b/process.c
@@ -1602,7 +1602,7 @@ rb_execarg_addopt(struct rb_exec_arg *e, VALUE key, VALUE val)
             if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_UMASK))) {
                 rb_raise(rb_eArgError, "umask option specified twice");
             }
-            rb_ary_store(options, EXEC_OPTION_UMASK, LONG2NUM(cmask));
+            rb_ary_store(options, EXEC_OPTION_UMASK, LONG2FIX(cmask));
         }
         else if (id == rb_intern("close_others")) {
             if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_CLOSE_OTHERS))) {