diff --git a/lib/oga/lexer.rl b/lib/oga/lexer.rl
index 1f4675d..66f7de5 100644
--- a/lib/oga/lexer.rl
+++ b/lib/oga/lexer.rl
@@ -302,9 +302,17 @@ module Oga
         element_name
           %{
             t(:T_ATTR, @ts, p)
-            advance_column
           }
-        '=' (dquote @string_dquote | squote @string_squote);
+
+        # The value of the attribute. Attribute values are not required. e.g.
+        # in <p data-foo></p> data-foo would be a boolean attribute.
+        (
+          '=' >{ advance_column }
+
+          # The value of the attribute, wrapped in either single or double
+          # quotes.
+          (dquote @string_dquote | squote @string_squote)
+        )*;
 
         # Non self-closing elements.
         '</' => {
diff --git a/spec/oga/lexer/elements_spec.rb b/spec/oga/lexer/elements_spec.rb
index 467cda1..a7deee5 100644
--- a/spec/oga/lexer/elements_spec.rb
+++ b/spec/oga/lexer/elements_spec.rb
@@ -25,6 +25,17 @@ describe Oga::Lexer do
         [:T_ELEM_CLOSE, nil, 1, 9]
       ]
     end
+  end
+
+  context 'elements with attributes' do
+    example 'lex an element with an attribute without a value' do
+      lex('<p foo></p>').should == [
+        [:T_ELEM_OPEN, nil, 1, 1],
+        [:T_ELEM_NAME, 'p', 1, 2],
+        [:T_ATTR, 'foo', 1, 4],
+        [:T_ELEM_CLOSE, nil, 1, 8]
+      ]
+    end
 
     example 'lex a paragraph element with attributes' do
       lex('<p class="foo">Hello</p>').should == [