diff --git a/elementpath/datatypes.py b/elementpath/datatypes.py
index 99b4ad0..cb7d318 100644
--- a/elementpath/datatypes.py
+++ b/elementpath/datatypes.py
@@ -1050,7 +1050,7 @@ QNAME_PATTERN = re.compile(
 )
 HEX_BINARY_PATTERN = re.compile(r'^[0-9a-fA-F]+$')
 NOT_BASE64_BINARY_PATTERN = re.compile(r'[^0-9a-zA-z+/= \t\n]')
-LANGUAGE_CODE_PATTERN = re.compile(r'^([a-zA-Z]{2}|[iI]-[a-zA-Z]+|[xX]-[a-zA-Z]{1,8})(-[a-zA-Z]{1,8})*$')
+LANGUAGE_CODE_PATTERN = re.compile(r'^[a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})*$')
 WRONG_ESCAPE_PATTERN = re.compile(r'%(?![a-eA-E\d]{2})')
 
 
diff --git a/elementpath/xpath_token.py b/elementpath/xpath_token.py
index 1caa038..c60e2f4 100644
--- a/elementpath/xpath_token.py
+++ b/elementpath/xpath_token.py
@@ -275,14 +275,16 @@ class XPathToken(Token):
         results = list(self.select(context))
         if len(results) == 1:
             res = results[0]
-            if isinstance(res, tuple) or is_etree_element(res) or is_document_node(res):
+            if isinstance(res, (bool, int, float, Decimal)):
+                return res
+            elif isinstance(res, tuple) or is_etree_element(res) or is_document_node(res):
+                return results
+            elif is_schema_node(res):
                 return results
             elif self.symbol in ('text', 'node'):
                 return results
             elif self.label in ('function', 'literal'):
                 return res
-            elif isinstance(res, bool):  # Tests and comparisons
-                return res
             else:
                 return results
         else:
@@ -483,13 +485,15 @@ class XPathToken(Token):
         of the node. Used for schema-based dynamic evaluation of XPath expressions.
         """
         try:
-            if obj.type.is_simple():
+            if obj.type.is_simple() or obj.type.has_simple_content():
                 # In case of schema element or attribute use a the sample value
                 # of the primitive type
                 primitive_type = self.parser.schema.get_primitive_type(obj.type)
                 return XSD_BUILTIN_TYPES[primitive_type.local_name].value
             elif obj.type.local_name == 'anyType':
                 return XSD_BUILTIN_TYPES['anyType'].value
+            else:
+                return UntypedAtomic('')
         except AttributeError:
             raise self.wrong_type("the argument %r is not a node of an XSD schema" % obj)
 
diff --git a/tests/test_xpath1_parser.py b/tests/test_xpath1_parser.py
index 7816700..e8f374e 100644
--- a/tests/test_xpath1_parser.py
+++ b/tests/test_xpath1_parser.py
@@ -839,13 +839,13 @@ class XPath1ParserTest(unittest.TestCase):
         root = self.etree.XML(XML_DATA_TEST)
         if self.parser.version == '1.0':
             self.check_value("'9' + 5.0", 14)
-            self.check_selector("/values/a + 2", root, [5.4])
+            self.check_selector("/values/a + 2", root, 5.4)
             self.check_value("/values/b + 2", float('nan'), context=XPathContext(root))
         else:
             self.check_selector("/values/a + 2", root, TypeError)
             self.check_value("/values/b + 2", TypeError, context=XPathContext(root))
 
-        self.check_selector("/values/d + 3", root, [47])
+        self.check_selector("/values/d + 3", root, 47)
 
     def test_numerical_mod_operator(self):
         self.check_value("11 mod 3", 2)
@@ -854,13 +854,13 @@ class XPath1ParserTest(unittest.TestCase):
 
         root = self.etree.XML(XML_DATA_TEST)
         if self.parser.version == '1.0':
-            self.check_selector("/values/a mod 2", root, [1.4])
+            self.check_selector("/values/a mod 2", root, 1.4)
             self.check_value("/values/b mod 2", float('nan'), context=XPathContext(root))
         else:
             self.check_selector("/values/a mod 2", root, TypeError)
             self.check_value("/values/b mod 2", TypeError, context=XPathContext(root))
 
-        self.check_selector("/values/d mod 3", root, [2])
+        self.check_selector("/values/d mod 3", root, 2)
 
     def test_number_function(self):
         root = self.etree.XML('<root>15</root>')
@@ -1145,13 +1145,14 @@ class LxmlXPath1ParserTest(XPath1ParserTest):
         else:
             results = select(root, path, namespaces, self.parser.__class__, **kwargs)
             variables = kwargs.get('variables', {})
+            if namespaces and '' in namespaces:
+                namespaces = {k: v for k, v in namespaces.items() if k}
+
             if isinstance(expected, set):
-                if namespaces and '' not in namespaces:
-                    self.assertEqual(set(root.xpath(path, namespaces=namespaces, **variables)), expected)
+                self.assertEqual(set(root.xpath(path, namespaces=namespaces, **variables)), expected)
                 self.assertEqual(set(results), expected)
             elif not callable(expected):
-                if namespaces and '' not in namespaces:
-                    self.assertEqual(root.xpath(path, namespaces=namespaces, **variables), expected)
+                self.assertEqual(root.xpath(path, namespaces=namespaces, **variables), expected)
                 self.assertEqual(results, expected)
             elif isinstance(expected, type):
                 self.assertTrue(isinstance(results, expected))
diff --git a/tests/test_xpath2_parser.py b/tests/test_xpath2_parser.py
index bbcc82a..5ac4faa 100644
--- a/tests/test_xpath2_parser.py
+++ b/tests/test_xpath2_parser.py
@@ -657,7 +657,9 @@ class XPath2ParserTest(test_xpath1_parser.XPath1ParserTest):
         self.check_value('xs:language(" en ")', "en")
         self.check_value('xs:language(" en-GB ")', "en-GB")
         self.check_value('xs:language("it-IT")', "it-IT")
-        self.wrong_value('xs:language("hello-world")')
+        self.check_value('xs:language("i-klingon")', 'i-klingon')  # IANA-registered language
+        self.check_value('xs:language("x-another-language-code")', 'x-another-language-code')
+        self.wrong_value('xs:language("MoreThan8")')
         self.check_value('xs:language(())', [])
 
         self.check_value('xs:NMTOKEN(" :menù.09-_ ")', ":menù.09-_")