diff --git a/lib/net/http/digest_auth.rb b/lib/net/http/digest_auth.rb
index 98feecb..6d3ce40 100644
--- a/lib/net/http/digest_auth.rb
+++ b/lib/net/http/digest_auth.rb
@@ -70,6 +70,10 @@ def initialize ignored = :ignored
   #
   # See Net::HTTP::DigestAuth for a complete example.
   #
+  # Raises an Net::HTTP::DigestAuth::Error if there is a syntax error
+  # in the +www_authenticate+ header or it does not include the Digest
+  # authentication method.
+  #
   # IIS servers handle the "qop" parameter of digest authentication
   # differently so you may need to set +iis+ to true for such servers.
 
@@ -79,12 +83,15 @@ def auth_header uri, www_authenticate, method, iis = false
     user     = CGI.unescape uri.user
     password = CGI.unescape uri.password
 
-    www_authenticate =~ /^(\w+) (.*)/
-
-    challenge = $2
+    if www_authenticate =~ /Digest ((?:\w+=(?:"[^"]+?"|[^\s,]+)(?:,\s?)?)+)/
+      challenge = $1
+    else
+      raise Error, "Digest auth method not found or syntax error in " +
+                   "auth header: #{www_authenticate}"
+    end
 
     params = {}
-    challenge.gsub(/(\w+)="(.*?)"/) { params[$1] = $2 }
+    challenge.gsub(/(\w+)=(?:"([^"]+?)"|([^\s,]+))/) { params[$1] = $2 || $3 }
 
     challenge =~ /algorithm="?(.*?)"?([, ]|$)/
 
diff --git a/test/test_net_http_digest_auth.rb b/test/test_net_http_digest_auth.rb
index 7fe0e61..c5a09e2 100644
--- a/test/test_net_http_digest_auth.rb
+++ b/test/test_net_http_digest_auth.rb
@@ -54,6 +54,22 @@ def test_auth_header_iis
     assert_equal expected, @da.auth_header(@uri, @header, 'GET', true)
   end
 
+  def test_auth_header_multi
+    multi_header = "NTLM, #{@header}, Basic realm=\"www.example.com\""
+
+    assert_equal expected, @da.auth_header(@uri, multi_header, 'GET')
+  end
+
+  def test_auth_header_unquoted_unspaced
+    header = [
+      'Digest qop=auth',
+      'realm="www.example.com"',
+      'nonce=4107baa081a592a6021660200000cd6c5686ff5f579324402b374d83e2c9'
+    ].join ','
+
+    assert_equal expected, @da.auth_header(@uri, header, 'GET')
+  end
+
   def test_auth_header_no_qop
     @header.sub! ' qop="auth",', ''
 
@@ -112,6 +128,26 @@ def test_auth_header_quoted_algorithm
     assert_equal expected, @da.auth_header(@uri, @header, 'GET')
   end
 
+  def test_auth_header_error
+    no_digest_auth_header = "Basic realm=\"www.example.com\""
+    erroneous_header = @header.gsub('=', '')
+
+    e = assert_raises Net::HTTP::DigestAuth::Error do
+      @da.auth_header(@uri, no_digest_auth_header, 'GET')
+    end
+
+    assert_equal "Digest auth method not found or syntax error in " +
+                 "auth header: #{no_digest_auth_header}",
+                 e.message
+
+    e = assert_raises Net::HTTP::DigestAuth::Error do
+      @da.auth_header(@uri, erroneous_header, 'GET')
+    end
+
+    assert_equal "Digest auth method not found or syntax error in " +
+                 "auth header: #{erroneous_header}", e.message
+  end
+
   def test_make_cnonce
     da = Net::HTTP::DigestAuth.new