diff --git a/CHANGELOG.md b/CHANGELOG.md
index 468f36f..8c98a83 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,11 @@
+## v3.0.0
+
+* Allow for OmniAuth 2.0 series. (#16)
+
+## v2.5.1
+
+* Add dependency constraint for omniauth 1.x (#16)
+
 ## v2.5.0
 
 * Added Slack v2 API support (oauth flow, scopes, tokens).
diff --git a/lib/omniauth-slack/version.rb b/lib/omniauth-slack/version.rb
index 443dbe3..2533085 100644
--- a/lib/omniauth-slack/version.rb
+++ b/lib/omniauth-slack/version.rb
@@ -1,5 +1,5 @@
 module OmniAuth
   module Slack
-    VERSION = "2.5.0"
+    VERSION = "3.0.0"
   end
 end
diff --git a/lib/omniauth/strategies/slack.rb b/lib/omniauth/strategies/slack.rb
index 38b3892..10cda4f 100644
--- a/lib/omniauth/strategies/slack.rb
+++ b/lib/omniauth/strategies/slack.rb
@@ -196,7 +196,7 @@ def client
       # some errors in call to /api/oauth.[v2.]access.
       #
       def callback_url
-        options.redirect_uri || full_host + script_name + callback_path
+        options.redirect_uri || full_host + callback_path
       end
       
       ### Possibly obsolete
diff --git a/omniauth-slack.gemspec b/omniauth-slack.gemspec
index 7e6396e..7e579e7 100644
--- a/omniauth-slack.gemspec
+++ b/omniauth-slack.gemspec
@@ -16,7 +16,8 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ['lib']
 
-  spec.add_runtime_dependency 'omniauth-oauth2', '>= 1.4.0'
+  spec.add_runtime_dependency 'omniauth', '~> 2.0'
+  spec.add_runtime_dependency 'omniauth-oauth2', '~> 1.7.1'
 
   spec.add_development_dependency 'bundler', '>= 1.11.2'
   spec.add_development_dependency 'rake'
diff --git a/test/strategy_test.rb b/test/strategy_test.rb
index 8a5f206..c4a6e91 100644
--- a/test/strategy_test.rb
+++ b/test/strategy_test.rb
@@ -94,6 +94,13 @@ class CallbackUrlTest < StrategyTestCase
     strategy.stubs(:script_name).returns("") # as not to depend on Rack env
     assert_equal "#{url_base}/auth/slack/done", strategy.callback_url
   end
+
+  test "returns callback_url when setting script_name" do
+    url_base = "http://auth.request.com"
+    @request.stubs(:url).returns("#{url_base}/page/path")
+    strategy.stubs(:script_name).returns("/foo") # as not to depend on Rack env
+    assert_equal "#{url_base}/foo/auth/slack/callback", strategy.callback_url
+  end
 end
 
 class UidTest < StrategyTestCase