diff --git a/lib/proxy_fetcher/document/adapters.rb b/lib/proxy_fetcher/document/adapters.rb
index 4ef6bb8..fb4bb1b 100644
--- a/lib/proxy_fetcher/document/adapters.rb
+++ b/lib/proxy_fetcher/document/adapters.rb
@@ -6,6 +6,8 @@ class Adapters
 
       class << self
         def lookup(name_or_class)
+          raise Exceptions::BlankAdapter if name_or_class.nil? || name_or_class.to_s.empty?
+
           case name_or_class
           when Symbol, String
             adapter_name = name_or_class.to_s.capitalize << ADAPTER
diff --git a/lib/proxy_fetcher/exceptions.rb b/lib/proxy_fetcher/exceptions.rb
index 08ef3b4..6a89e4d 100644
--- a/lib/proxy_fetcher/exceptions.rb
+++ b/lib/proxy_fetcher/exceptions.rb
@@ -39,6 +39,16 @@ def initialize(name)
       end
     end
 
+    class BlankAdapter < Error
+      def initialize(*)
+        super(<<-MSG.strip.squeeze
+          you need to specify adapter for HTML parsing: ProxyFetcher.config.adapter = :nokogiri.
+          You can use one of the predefined adapters (:nokogiri or :oga) or your own implementation.
+          MSG
+        )
+      end
+    end
+
     class AdapterSetupError < Error
       def initialize(adapter_name, reason)
         adapter = demodulize(adapter_name.remove('Adapter'))
diff --git a/lib/proxy_fetcher/providers/http_tunnel.rb b/lib/proxy_fetcher/providers/http_tunnel.rb
index f42dd42..ed991b5 100644
--- a/lib/proxy_fetcher/providers/http_tunnel.rb
+++ b/lib/proxy_fetcher/providers/http_tunnel.rb
@@ -1,5 +1,3 @@
-require 'irb'
-
 module ProxyFetcher
   module Providers
     class HTTPTunnel < Base
diff --git a/proxy_fetcher.gemspec b/proxy_fetcher.gemspec
index 16f7ea3..a53640d 100644
--- a/proxy_fetcher.gemspec
+++ b/proxy_fetcher.gemspec
@@ -5,10 +5,10 @@ require 'proxy_fetcher/version'
 Gem::Specification.new do |gem|
   gem.name = 'proxy_fetcher'
   gem.version = ProxyFetcher.gem_version
-  gem.date = '2017-11-13'
+  gem.date = '2017-12-05'
   gem.summary = 'Ruby gem for dealing with proxy lists from different providers'
   gem.description = 'This gem can help your Ruby application to make HTTP(S) requests ' \
-                    'from proxy server by fetching and validating proxy lists from the different providers.'
+                    'using proxies by fetching and validating proxy lists from the different providers.'
   gem.authors = ['Nikita Bulai']
   gem.email = 'bulajnikita@gmail.com'
   gem.require_paths = ['lib']
diff --git a/spec/proxy_fetcher/document/adapters_spec.rb b/spec/proxy_fetcher/document/adapters_spec.rb
index 5b18683..f203846 100644
--- a/spec/proxy_fetcher/document/adapters_spec.rb
+++ b/spec/proxy_fetcher/document/adapters_spec.rb
@@ -12,6 +12,11 @@
       expect(described_class.lookup(Struct)).to eq(Struct)
     end
 
+    it 'raises an exception if passed value is blank' do
+      expect { described_class.lookup(nil) }.to raise_error(ProxyFetcher::Exceptions::BlankAdapter)
+      expect { described_class.lookup('') }.to raise_error(ProxyFetcher::Exceptions::BlankAdapter)
+    end
+
     it "raises an exception if adapter doesn't exist" do
       expect { described_class.lookup('wrong') }.to raise_error(ProxyFetcher::Exceptions::UnknownAdapter)
     end