diff --git a/lib/oga/css/lexer.rl b/lib/oga/css/lexer.rl
index 24d8512..1878391 100644
--- a/lib/oga/css/lexer.rl
+++ b/lib/oga/css/lexer.rl
@@ -239,12 +239,16 @@ module Oga
         pseudo_args := |*
           whitespace;
 
-          nth     => { add_token(:T_NTH) };
-          minus   => { add_token(:T_MINUS) };
-          odd     => { add_token(:T_ODD) };
-          even    => { add_token(:T_EVEN) };
-          integer => emit_integer;
-          rparen  => emit_rparen;
+          # NOTE: the priorities here are put in place to ensure that rules such
+          # as  `nth` take precedence over `identifier`. The highest number has
+          # the highest priority.
+          nth > 5        => { add_token(:T_NTH) };
+          minus          => { add_token(:T_MINUS) };
+          odd > 4        => { add_token(:T_ODD) };
+          even > 3       => { add_token(:T_EVEN) };
+          integer > 2    => emit_integer;
+          rparen         => emit_rparen;
+          identifier > 1 => emit_identifier;
         *|;
 
         # Predicates
diff --git a/lib/oga/css/parser.y b/lib/oga/css/parser.y
index 5379d15..43382ca 100644
--- a/lib/oga/css/parser.y
+++ b/lib/oga/css/parser.y
@@ -142,6 +142,7 @@ rule
     | odd
     | even
     | nth
+    | node_test
     ;
 
   odd
diff --git a/spec/oga/css/lexer/pseudo_classes_spec.rb b/spec/oga/css/lexer/pseudo_classes_spec.rb
index 772b976..c075588 100644
--- a/spec/oga/css/lexer/pseudo_classes_spec.rb
+++ b/spec/oga/css/lexer/pseudo_classes_spec.rb
@@ -116,5 +116,15 @@ describe Oga::CSS::Lexer do
         [:T_RPAREN, nil]
       ]
     end
+
+    example 'lex the :lang(fr) pseudo class' do
+      lex_css(':lang(fr)').should == [
+        [:T_COLON, nil],
+        [:T_IDENT, 'lang'],
+        [:T_LPAREN, nil],
+        [:T_IDENT, 'fr'],
+        [:T_RPAREN, nil]
+      ]
+    end
   end
 end
diff --git a/spec/oga/css/parser/pseudo_classes_spec.rb b/spec/oga/css/parser/pseudo_classes_spec.rb
index 0466b0b..b738993 100644
--- a/spec/oga/css/parser/pseudo_classes_spec.rb
+++ b/spec/oga/css/parser/pseudo_classes_spec.rb
@@ -107,5 +107,14 @@ describe Oga::CSS::Parser do
         s(:pseudo, 'focus', s(:test, nil, 'x'))
       )
     end
+
+    example 'parse a pseudo class with an identifier as the argument' do
+      parse_css('x:lang(fr)').should == s(
+        :pseudo,
+        'lang',
+        s(:test, nil, 'x'),
+        s(:test, nil, 'fr')
+      )
+    end
   end
 end