diff --git a/ChangeLog b/ChangeLog
index 4784bffadb..04274958b4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Mar 31 13:20:40 2012  Sokolov Yura (funny-falcon)  <funny.falcon@gmail.com>
+
+	* hash.c: remove unnecessary checks for Qundef in hash iterations.
+	  since hash use st_foreach_check for iterations, such checks are
+	  needless.
+
 Sat Mar 31 12:05:01 2012  Martin Bosslet  <Martin.Bosslet@googlemail.com>
 
 	* ext/openssl/ossl_x509cert.c: Fix doc typo.
diff --git a/ext/-test-/st/numhash/numhash.c b/ext/-test-/st/numhash/numhash.c
index c746ac5495..d4dbd1a0ce 100644
--- a/ext/-test-/st/numhash/numhash.c
+++ b/ext/-test-/st/numhash/numhash.c
@@ -42,10 +42,9 @@ numhash_aset(VALUE self, VALUE key, VALUE data)
 }
 
 static int
-numhash_i(st_data_t key, st_data_t value, st_data_t arg, int error)
+numhash_i(st_data_t key, st_data_t value, st_data_t arg)
 {
     VALUE ret;
-    if (key == 0 && value == 0 && error == 1) rb_raise(rb_eRuntimeError, "numhash modified");
     ret = rb_yield_values(3, (VALUE)key, (VALUE)value, (VALUE)arg);
     if (ret == Qtrue) return ST_CHECK;
     return ST_CONTINUE;
diff --git a/hash.c b/hash.c
index b6c4dbd974..1ed3870283 100644
--- a/hash.c
+++ b/hash.c
@@ -145,7 +145,7 @@ struct hash_foreach_arg {
 };
 
 static int
-hash_foreach_iter(st_data_t key, st_data_t value, st_data_t argp, int err)
+hash_foreach_iter(st_data_t key, st_data_t value, st_data_t argp)
 {
     struct hash_foreach_arg *arg = (struct hash_foreach_arg *)argp;
     int status;
@@ -437,7 +437,7 @@ rb_hash_rehash_i(VALUE key, VALUE value, VALUE arg)
 {
     st_table *tbl = (st_table *)arg;
 
-    if (key != Qundef) st_insert(tbl, (st_data_t)key, (st_data_t)value);
+    st_insert(tbl, (st_data_t)key, (st_data_t)value);
     return ST_CONTINUE;
 }
 
@@ -874,7 +874,6 @@ rb_hash_shift(VALUE hash)
 static int
 delete_if_i(VALUE key, VALUE value, VALUE hash)
 {
-    if (key == Qundef) return ST_CONTINUE;
     if (RTEST(rb_yield_values(2, key, value))) {
 	rb_hash_delete_key(hash, key);
     }
@@ -972,7 +971,6 @@ rb_hash_values_at(int argc, VALUE *argv, VALUE hash)
 static int
 select_i(VALUE key, VALUE value, VALUE result)
 {
-    if (key == Qundef) return ST_CONTINUE;
     if (RTEST(rb_yield_values(2, key, value)))
 	rb_hash_aset(result, key, value);
     return ST_CONTINUE;
@@ -1006,7 +1004,6 @@ rb_hash_select(VALUE hash)
 static int
 keep_if_i(VALUE key, VALUE value, VALUE hash)
 {
-    if (key == Qundef) return ST_CONTINUE;
     if (!RTEST(rb_yield_values(2, key, value))) {
 	return ST_DELETE;
     }
@@ -1132,9 +1129,7 @@ rb_hash_aset(VALUE hash, VALUE key, VALUE val)
 static int
 replace_i(VALUE key, VALUE val, VALUE hash)
 {
-    if (key != Qundef) {
-	rb_hash_aset(hash, key, val);
-    }
+    rb_hash_aset(hash, key, val);
 
     return ST_CONTINUE;
 }
@@ -1215,7 +1210,6 @@ rb_hash_empty_p(VALUE hash)
 static int
 each_value_i(VALUE key, VALUE value)
 {
-    if (key == Qundef) return ST_CONTINUE;
     rb_yield(value);
     return ST_CONTINUE;
 }
@@ -1250,7 +1244,6 @@ rb_hash_each_value(VALUE hash)
 static int
 each_key_i(VALUE key, VALUE value)
 {
-    if (key == Qundef) return ST_CONTINUE;
     rb_yield(key);
     return ST_CONTINUE;
 }
@@ -1284,7 +1277,6 @@ rb_hash_each_key(VALUE hash)
 static int
 each_pair_i(VALUE key, VALUE value)
 {
-    if (key == Qundef) return ST_CONTINUE;
     rb_yield(rb_assoc_new(key, value));
     return ST_CONTINUE;
 }
@@ -1322,7 +1314,6 @@ rb_hash_each_pair(VALUE hash)
 static int
 to_a_i(VALUE key, VALUE value, VALUE ary)
 {
-    if (key == Qundef) return ST_CONTINUE;
     rb_ary_push(ary, rb_assoc_new(key, value));
     return ST_CONTINUE;
 }
@@ -1355,7 +1346,6 @@ inspect_i(VALUE key, VALUE value, VALUE str)
 {
     VALUE str2;
 
-    if (key == Qundef) return ST_CONTINUE;
     str2 = rb_inspect(key);
     if (RSTRING_LEN(str) > 1) {
 	rb_str_cat2(str, ", ");
@@ -1422,7 +1412,6 @@ rb_hash_to_hash(VALUE hash)
 static int
 keys_i(VALUE key, VALUE value, VALUE ary)
 {
-    if (key == Qundef) return ST_CONTINUE;
     rb_ary_push(ary, key);
     return ST_CONTINUE;
 }
@@ -1453,7 +1442,6 @@ rb_hash_keys(VALUE hash)
 static int
 values_i(VALUE key, VALUE value, VALUE ary)
 {
-    if (key == Qundef) return ST_CONTINUE;
     rb_ary_push(ary, value);
     return ST_CONTINUE;
 }
@@ -1512,7 +1500,6 @@ rb_hash_search_value(VALUE key, VALUE value, VALUE arg)
 {
     VALUE *data = (VALUE *)arg;
 
-    if (key == Qundef) return ST_CONTINUE;
     if (rb_equal(value, data[1])) {
 	data[0] = Qtrue;
 	return ST_STOP;
@@ -1556,7 +1543,6 @@ eql_i(VALUE key, VALUE val1, VALUE arg)
     struct equal_data *data = (struct equal_data *)arg;
     st_data_t val2;
 
-    if (key == Qundef) return ST_CONTINUE;
     if (!st_lookup(data->tbl, key, &val2)) {
 	data->result = Qfalse;
 	return ST_STOP;
@@ -1658,7 +1644,6 @@ hash_i(VALUE key, VALUE val, VALUE arg)
     st_index_t *hval = (st_index_t *)arg;
     st_index_t hdata[2];
 
-    if (key == Qundef) return ST_CONTINUE;
     hdata[0] = rb_hash(key);
     hdata[1] = rb_hash(val);
     *hval ^= st_hash(hdata, sizeof(hdata), 0);
@@ -1699,7 +1684,6 @@ rb_hash_hash(VALUE hash)
 static int
 rb_hash_invert_i(VALUE key, VALUE value, VALUE hash)
 {
-    if (key == Qundef) return ST_CONTINUE;
     rb_hash_aset(hash, value, key);
     return ST_CONTINUE;
 }
@@ -1728,7 +1712,6 @@ rb_hash_invert(VALUE hash)
 static int
 rb_hash_update_i(VALUE key, VALUE value, VALUE hash)
 {
-    if (key == Qundef) return ST_CONTINUE;
     hash_update(hash, key);
     st_insert(RHASH(hash)->ntbl, key, value);
     return ST_CONTINUE;
@@ -1737,7 +1720,6 @@ rb_hash_update_i(VALUE key, VALUE value, VALUE hash)
 static int
 rb_hash_update_block_i(VALUE key, VALUE value, VALUE hash)
 {
-    if (key == Qundef) return ST_CONTINUE;
     if (rb_hash_has_key(hash, key)) {
 	value = rb_yield_values(3, key, rb_hash_aref(hash, key), value);
     }
@@ -1794,7 +1776,6 @@ rb_hash_update_func_i(VALUE key, VALUE value, VALUE arg0)
     struct update_arg *arg = (struct update_arg *)arg0;
     VALUE hash = arg->hash;
 
-    if (key == Qundef) return ST_CONTINUE;
     if (rb_hash_has_key(hash, key)) {
 	value = (*arg->func)(key, rb_hash_aref(hash, key), value);
     }
@@ -1851,7 +1832,6 @@ assoc_i(VALUE key, VALUE val, VALUE arg)
 {
     VALUE *args = (VALUE *)arg;
 
-    if (key == Qundef) return ST_CONTINUE;
     if (RTEST(rb_equal(args[0], key))) {
 	args[1] = rb_assoc_new(key, val);
 	return ST_STOP;
@@ -1889,7 +1869,6 @@ rassoc_i(VALUE key, VALUE val, VALUE arg)
 {
     VALUE *args = (VALUE *)arg;
 
-    if (key == Qundef) return ST_CONTINUE;
     if (RTEST(rb_equal(args[0], val))) {
 	args[1] = rb_assoc_new(key, val);
 	return ST_STOP;
@@ -3086,11 +3065,9 @@ env_invert(void)
 static int
 env_replace_i(VALUE key, VALUE val, VALUE keys)
 {
-    if (key != Qundef) {
-	env_aset(Qnil, key, val);
-	if (rb_ary_includes(keys, key)) {
-	    rb_ary_delete(keys, key);
-	}
+    env_aset(Qnil, key, val);
+    if (rb_ary_includes(keys, key)) {
+	rb_ary_delete(keys, key);
     }
     return ST_CONTINUE;
 }
@@ -3122,12 +3099,10 @@ env_replace(VALUE env, VALUE hash)
 static int
 env_update_i(VALUE key, VALUE val)
 {
-    if (key != Qundef) {
-	if (rb_block_given_p()) {
-	    val = rb_yield_values(3, key, rb_f_getenv(Qnil, key), val);
-	}
-	env_aset(Qnil, key, val);
+    if (rb_block_given_p()) {
+	val = rb_yield_values(3, key, rb_f_getenv(Qnil, key), val);
     }
+    env_aset(Qnil, key, val);
     return ST_CONTINUE;
 }