diff --git a/lib/oga/css/parser.y b/lib/oga/css/parser.y
index e113b2c..54ca342 100644
--- a/lib/oga/css/parser.y
+++ b/lib/oga/css/parser.y
@@ -97,9 +97,12 @@ rule
   class
     : T_DOT T_IDENT
       {
+        axis = s(:axis, 'attribute', s(:test, nil, 'class'))
+
         s(
-          :eq,
-          s(:axis, 'attribute', s(:test, nil, 'class')),
+          :call,
+          'contains',
+          s(:call, 'concat', s(:string, ' '), axis, s(:string, ' ')),
           s(:string, val[1])
         )
       }
diff --git a/spec/oga/css/parser/classes_spec.rb b/spec/oga/css/parser/classes_spec.rb
index 7cf0289..9bb421d 100644
--- a/spec/oga/css/parser/classes_spec.rb
+++ b/spec/oga/css/parser/classes_spec.rb
@@ -4,25 +4,27 @@ describe Oga::CSS::Parser do
   context 'classes' do
     example 'parse a class selector' do
       parse_css('.foo').should == parse_xpath(
-        'descendant-or-self::*[@class="foo"]'
+        'descendant-or-self::*[contains(concat(" ", @class, " "), "foo")]'
       )
     end
 
     example 'parse a selector for an element with a class' do
       parse_css('foo.bar').should == parse_xpath(
-        'descendant-or-self::foo[@class="bar"]'
+        'descendant-or-self::foo[contains(concat(" ", @class, " "), "bar")]'
       )
     end
 
     example 'parse a selector using multiple classes' do
       parse_css('.foo.bar').should == parse_xpath(
-        'descendant-or-self::*[@class="foo" and @class="bar"]'
+        'descendant-or-self::*[contains(concat(" ", @class, " "), "foo") ' \
+          'and contains(concat(" ", @class, " "), "bar")]'
       )
     end
 
     example 'parse a selector using a class and an ID' do
       parse_css('#foo.bar').should == parse_xpath(
-        'descendant-or-self::*[@id="foo" and @class="bar"]'
+        'descendant-or-self::*[@id="foo" and ' \
+          'contains(concat(" ", @class, " "), "bar")]'
       )
     end
   end
diff --git a/spec/oga/css/parser/ids_spec.rb b/spec/oga/css/parser/ids_spec.rb
index cc6ef6a..42876b0 100644
--- a/spec/oga/css/parser/ids_spec.rb
+++ b/spec/oga/css/parser/ids_spec.rb
@@ -22,7 +22,8 @@ describe Oga::CSS::Parser do
 
     example 'parse a selector using an ID and a class' do
       parse_css('.foo#bar').should == parse_xpath(
-        'descendant-or-self::*[@class="foo" and @id="bar"]'
+        'descendant-or-self::*[contains(concat(" ", @class, " "), "foo") ' \
+          'and @id="bar"]'
       )
     end
   end