diff --git a/Gemfile b/Gemfile
index 2573d3f..054a91d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,6 +2,7 @@ source 'https://rubygems.org'
 gemspec
 
 gem 'json', '~>2.0', platforms: %i[mri_18 jruby]
+gem 'logger'
 
 gem 'rdf', '~>3.0'
 gem 'rdf-vocab', '~>3.0'
diff --git a/Gemfile.lock b/Gemfile.lock
index 174f602..c8287cb 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -53,6 +53,7 @@ GEM
     json (2.7.1-java)
     latex-decode (0.4.0)
     link_header (0.0.8)
+    logger (1.7.0)
     mini_mime (1.1.5)
     minitest (5.20.0)
     multi_test (1.1.0)
@@ -99,6 +100,7 @@ DEPENDENCIES
   gnuplot
   iconv
   json (~> 2.0)
+  logger
   minitest
   rake
   rdf (~> 3.0)
diff --git a/lib/bibtex/lexer.rb b/lib/bibtex/lexer.rb
index ff57337..60256ed 100644
--- a/lib/bibtex/lexer.rb
+++ b/lib/bibtex/lexer.rb
@@ -58,8 +58,8 @@ class Lexer
       string: /string/io,
       comment: /comment\b/io,
       preamble: /preamble\b/io,
-      key: %r{\s*[[:alpha:][:digit:] /:_!$\?\.%+;&\*'"-]+,}io,
-      optional_key: %r{\s*[[:alpha:][:digit:] /:_!$\?\.%+;&\*'"-]*,}io
+      key: %r{\s*[[:alpha:][:digit:] /:_!$\?\.%+;&\*'"{}-]+,}io,
+      optional_key: %r{\s*[[:alpha:][:digit:] /:_!$\?\.%+;&\*'"{}-]*,}io
     }
 
     MODE = Hash.new(:meta).merge(
@@ -120,7 +120,7 @@ def next_token
       @stack.shift
     end
 
-    # Returns true if the lexer is currenty parsing a BibTeX object.
+    # Returns true if the lexer is currently parsing a BibTeX object.
     def bibtex_mode?
       MODE[@mode] == :bibtex
     end
@@ -302,13 +302,12 @@ def enter_object
         @mode = @active_object = :entry
         push [:NAME, @scanner.matched]
 
-        # TODO: DRY - try to parse key
         if @scanner.scan(Lexer.patterns[:lbrace])
           @brace_level += 1
           push([:LBRACE, '{'])
           @mode = :content if @brace_level > 1 || @brace_level == 1 && active?(:comment)
 
-          push [:KEY, @scanner.matched.chop.strip] if @scanner.scan(Lexer.patterns[allow_missing_keys? ? :optional_key : :key])
+          parse_key
         end
 
       else
@@ -316,6 +315,13 @@ def enter_object
       end
     end
 
+    def parse_key
+      return unless @scanner.scan(Lexer.patterns[allow_missing_keys? ? :optional_key : :key])
+
+      key = @scanner.matched.chop.strip
+      push [:KEY, key]
+    end
+
     # Called when parser leaves a BibTeX object.
     def leave_object
       @mode = :meta
diff --git a/test/bibtex/test_lexer.rb b/test/bibtex/test_lexer.rb
index 7dc100b..5904c91 100644
--- a/test/bibtex/test_lexer.rb
+++ b/test/bibtex/test_lexer.rb
@@ -7,33 +7,37 @@ class LexerTest < Minitest::Spec
     end
 
     it 'strips line breaks by default' do
-      Lexer.new.analyse(%(@string{ x = "foo\nbar" })).stack[-3].must_be :==,
+      _(Lexer.new.analyse(%(@string{ x = "foo\nbar" })).stack[-3]).must_be :==,
                                                                         [:STRING_LITERAL, 'foo bar']
     end
 
     it 'strips whitespace after line breaks by default' do
-      Lexer.new.analyse(%(@string{ x = "foo\n    bar" })).stack[-3].must_be :==,
+      _(Lexer.new.analyse(%(@string{ x = "foo\n    bar" })).stack[-3]).must_be :==,
                                                                             [:STRING_LITERAL, 'foo bar']
     end
 
     it 'matches KEY tokens' do
-      Lexer.new.analyse('@misc{foo, }').symbols.must_be :==, [:AT, :NAME, :LBRACE, :KEY, :RBRACE, false]
+      _(Lexer.new.analyse('@misc{foo, }').symbols).must_be :==, [:AT, :NAME, :LBRACE, :KEY, :RBRACE, false]
     end
 
     it 'matches KEY tokens with non-ascii characters' do
-      Lexer.new.analyse('@misc{löwe, }').symbols.must_be :==, [:AT, :NAME, :LBRACE, :KEY, :RBRACE, false]
+      _(Lexer.new.analyse('@misc{löwe, }').symbols).must_be :==, [:AT, :NAME, :LBRACE, :KEY, :RBRACE, false]
     end
 
     it 'matches KEY tokens after whitespace' do
-      Lexer.new.analyse('@misc{  foo, }').symbols.must_be :==, [:AT, :NAME, :LBRACE, :KEY, :RBRACE, false]
+      _(Lexer.new.analyse('@misc{  foo, }').symbols).must_be :==, [:AT, :NAME, :LBRACE, :KEY, :RBRACE, false]
+    end
+
+    it 'matches KEY tokens with braces' do
+      _(Lexer.new.analyse('@misc{foo:{123}, }').symbols).must_be :==, [:AT, :NAME, :LBRACE, :KEY, :RBRACE, false]
     end
 
     it "doesn't start a comment for types starting with but not equal @comment" do
-      Lexer.new.analyse('@commentary{staudinger, }').symbols.must_be :==, [:AT, :NAME, :LBRACE, :KEY, :RBRACE, false]
+      _(Lexer.new.analyse('@commentary{staudinger, }').symbols).must_be :==, [:AT, :NAME, :LBRACE, :KEY, :RBRACE, false]
     end
 
     it "doesn't start a preamble for types starting with but not equal @preamble" do
-      Lexer.new.analyse('@preamblestring{ preamble }').symbols.must_be :==, [:AT, :NAME, :LBRACE, :NAME, :RBRACE, false]
+      _(Lexer.new.analyse('@preamblestring{ preamble }').symbols).must_be :==, [:AT, :NAME, :LBRACE, :NAME, :RBRACE, false]
     end
   end
 end
diff --git a/test/test_bibtex.rb b/test/test_bibtex.rb
index 3b9ffee..8701c88 100644
--- a/test/test_bibtex.rb
+++ b/test/test_bibtex.rb
@@ -101,19 +101,22 @@ def test_logger_can_be_assigned
     end
 
     def test_missing_key
-      assert_raises(BibTeX::ParseError) do
+      error = assert_raises(BibTeX::ParseError) do
         BibTeX.parse(<<EOF)
         @article{}
 EOF
       end
+      assert_equal('Failed to parse BibTeX entry: cite-key missing', error.message)
+
       assert(
         BibTeX.parse(<<EOF, allow_missing_keys: true)
         @article{}
 EOF
       )
+
       Timeout.timeout(2) do
         BibTeX.parse(<<EOF, allow_missing_keys: true)
-        @article{},
+        @article{foo, },
         @article{}
 EOF
       end