diff --git a/README.md b/README.md
index 9f27f7e..fad3f88 100644
--- a/README.md
+++ b/README.md
@@ -135,6 +135,8 @@ The service provider metadata used to ease configuration of the SAML SP in the I
   *Note*: All attributes can also be found in an array under `auth_hash[:extra][:raw_info]`,
   so this setting should only be used to map attributes that are part of the OmniAuth info hash schema.
 
+* `:uid_attribute` - Attribute that uniquely identifies the user. If unset, the name identifier returned by the IdP is used.
+
 * See the `OneLogin::RubySaml::Settings` class in the [Ruby SAML gem](https://github.com/onelogin/ruby-saml) for additional supported options.
 
 ## Devise Integration
diff --git a/lib/omniauth/strategies/saml.rb b/lib/omniauth/strategies/saml.rb
index d2e5ac7..0913ccb 100644
--- a/lib/omniauth/strategies/saml.rb
+++ b/lib/omniauth/strategies/saml.rb
@@ -28,6 +28,7 @@ def self.inherited(subclass)
         last_name: ["last_name", "lastname", "lastName"]
       }
       option :slo_default_relay_state
+      option :uid_attribute
 
       def request_phase
         options[:assertion_consumer_service_url] ||= callback_url
@@ -136,7 +137,17 @@ def other_phase
         end
       end
 
-      uid { @name_id }
+      uid do
+        if options.uid_attribute
+          ret = find_attribute_by([options.uid_attribute])
+          if ret.nil?
+            raise OmniAuth::Strategies::SAML::ValidationError.new("SAML response missing '#{options.uid_attribute}' attribute")
+          end
+          ret
+        else
+          @name_id
+        end
+      end
 
       info do
         found_attributes = options.attribute_statements.map do |key, values|
diff --git a/spec/omniauth/strategies/saml_spec.rb b/spec/omniauth/strategies/saml_spec.rb
index 85eeffb..d731b3b 100644
--- a/spec/omniauth/strategies/saml_spec.rb
+++ b/spec/omniauth/strategies/saml_spec.rb
@@ -207,6 +207,31 @@ def post_xml(xml=:example_response, opts = {})
       end
     end
 
+    context "when using custom user id attribute" do
+      before :each do
+        saml_options[:idp_cert_fingerprint] = "3B:82:F1:F5:54:FC:A8:FF:12:B8:4B:B8:16:61:1D:E4:8E:9B:E2:3C"
+        saml_options[:uid_attribute] = "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress"
+        post_xml :custom_attributes
+      end
+
+      it "should return user id attribute" do
+        expect(auth_hash[:uid]).to eq("user@example.com")
+      end
+    end
+
+    context "when using custom user id attribute, but it is missing" do
+      before :each do
+        saml_options[:uid_attribute] = "missing_attribute"
+        post_xml
+      end
+
+      it "should fail to authenticate" do
+        should fail_with(:invalid_ticket)
+        expect(last_request.env['omniauth.error']).to be_instance_of(OmniAuth::Strategies::SAML::ValidationError)
+        expect(last_request.env['omniauth.error'].message).to eq("SAML response missing 'missing_attribute' attribute")
+      end
+    end
+
     context "when response is a logout response" do
       before :each do
         saml_options[:issuer] = "https://idp.sso.example.com/metadata/29490"