diff --git a/ChangeLog b/ChangeLog
index d081251f5c..52be7c1e55 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Sat Apr 26 21:30:40 2008  Tanaka Akira  <akr@fsij.org>
+
+	* include/ruby/intern.h (rb_hash_dup): declared.
+
+	* hash.c (rb_hash_dup): new function.
+	
+	* process.c (rb_spawn_internal): don't modify option hash.
+
 Sat Apr 26 18:36:31 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* io.c, signal.c, thread.c, thread_win32.c, include/ruby/intern.h:
diff --git a/hash.c b/hash.c
index 006b5f85d8..89c470f9e4 100644
--- a/hash.c
+++ b/hash.c
@@ -228,6 +228,19 @@ rb_hash_new(void)
     return hash_alloc(rb_cHash);
 }
 
+VALUE
+rb_hash_dup(VALUE hash)
+{
+    VALUE ret = hash_alloc(RBASIC(hash)->klass);
+    if (!RHASH_EMPTY_P(hash))
+        RHASH(ret)->ntbl = st_copy(RHASH(hash)->ntbl);
+    if (FL_TEST(hash, HASH_PROC_DEFAULT)) {
+        FL_SET(ret, HASH_PROC_DEFAULT);
+    }
+    RHASH(ret)->ifnone = RHASH(hash)->ifnone;
+    return ret;
+}
+
 static void
 rb_hash_modify_check(VALUE hash)
 {
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 5272079df7..4df92419b4 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -344,6 +344,7 @@ void st_foreach_safe(struct st_table *, int (*)(ANYARGS), st_data_t);
 void rb_hash_foreach(VALUE, int (*)(ANYARGS), VALUE);
 VALUE rb_hash(VALUE);
 VALUE rb_hash_new(void);
+VALUE rb_hash_dup(VALUE);
 VALUE rb_hash_freeze(VALUE);
 VALUE rb_hash_aref(VALUE, VALUE);
 VALUE rb_hash_lookup(VALUE, VALUE);
diff --git a/process.c b/process.c
index cb0ab4f4ac..6a1b84fa5e 100644
--- a/process.c
+++ b/process.c
@@ -2560,6 +2560,10 @@ rb_spawn_internal(int argc, VALUE *argv, int default_close_others)
             opthash = rb_hash_new();
             RBASIC(opthash)->klass = 0;
         }
+        if (RBASIC(opthash)->klass) {
+            opthash = rb_hash_dup(opthash);
+            RBASIC(opthash)->klass = 0;
+        }
         if (!st_lookup(RHASH_TBL(opthash), close_others, 0))
             rb_hash_aset(opthash, close_others, Qtrue);
     }
diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index e68f1070e6..36cc5d14a7 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -500,6 +500,21 @@ class TestProcess < Test::Unit::TestCase
     }
   end
 
+  def test_execopts_modification
+    h = {}
+    Process.wait spawn(EnvUtil.rubybin, '-e', '', h)
+    assert_equal({}, h)
+
+    h = {}
+    system(EnvUtil.rubybin, '-e', '', h)
+    assert_equal({}, h)
+
+    h = {}
+    io = IO.popen([EnvUtil.rubybin, '-e', '', h])
+    io.close
+    assert_equal({}, h)
+  end
+
   def test_system
     str = "echo fofo"
     assert_nil(system([str, str]))