diff --git a/lib/casserver/authenticators/sql.rb b/lib/casserver/authenticators/sql.rb
index e86976b..0707619 100644
--- a/lib/casserver/authenticators/sql.rb
+++ b/lib/casserver/authenticators/sql.rb
@@ -54,8 +54,9 @@ end
 class CASServer::Authenticators::SQL < CASServer::Authenticators::Base
   def self.setup(options)
     raise CASServer::AuthenticatorError, "Invalid authenticator configuration!" unless options[:database]
-
-    user_model_name = "CASUser_#{options[:auth_index]}"
+    auth_index = options[:auth_index]
+    user_table = options[:user_table] || 'users'
+    user_model_name = "CASUser_#{auth_index}"
     $LOG.debug "CREATING USER MODEL #{user_model_name}"
 
     class_eval %{
@@ -63,24 +64,26 @@ class CASServer::Authenticators::SQL < CASServer::Authenticators::Base
       end
     }
 
-    @user_model = const_get(user_model_name)
-    @user_model.establish_connection(options[:database])
+    user_model = const_get(user_model_name)
+    # Register new user module, identified by auth_index.
+    user_models[auth_index] = user_model
+    user_model.establish_connection(options[:database])
     if ActiveRecord::VERSION::STRING >= '3.2'
-      @user_model.table_name = (options[:user_table] || 'users')
+      user_model.table_name = user_table
     else
-      @user_model.set_table_name(options[:user_table] || 'users')
+      user_model.set_table_name(user_table)
     end
-    @user_model.inheritance_column = 'no_inheritance_column' if options[:ignore_type_column]
+    user_model.inheritance_column = 'no_inheritance_column' if options[:ignore_type_column]
     begin
-     @user_model.connection
+     user_model.connection
     rescue => e
       $LOG.debug e
       raise "SQL Authenticator can not connect to database"
     end
   end
 
-  def self.user_model
-    @user_model
+  def self.user_models
+    @user_models ||= {}
   end
 
   def validate(credentials)
@@ -89,15 +92,16 @@ class CASServer::Authenticators::SQL < CASServer::Authenticators::Base
 
     log_connection_pool_size
     user_model.connection_pool.checkin(user_model.connection)
+    users = matching_users
 
-    if matching_users.size > 0
-      $LOG.warn("#{self.class}: Multiple matches found for user #{@username.inspect}") if matching_users.size > 1
+    if users.size > 0
+      $LOG.warn("#{self.class}: Multiple matches found for user #{@username.inspect}") if users.size > 1
 
       unless @options[:extra_attributes].blank?
-        if matching_users.size > 1
+        if users.size > 1
           $LOG.warn("#{self.class}: Unable to extract extra_attributes because multiple matches were found for #{@username.inspect}")
         else
-          user = matching_users.first
+          user = users.first
 
           extract_extra(user)
           log_extra
@@ -113,7 +117,11 @@ class CASServer::Authenticators::SQL < CASServer::Authenticators::Base
   protected
 
   def user_model
-    self.class.user_model
+    self.class.user_models[auth_index]
+  end
+
+  def auth_index
+    @options[:auth_index]
   end
 
   def username_column
diff --git a/spec/casserver/authenticators/sql_spec.rb b/spec/casserver/authenticators/sql_spec.rb
new file mode 100644
index 0000000..c935768
--- /dev/null
+++ b/spec/casserver/authenticators/sql_spec.rb
@@ -0,0 +1,116 @@
+require 'spec_helper'
+
+describe CASServer::Authenticators::SQL do
+  let(:options) do
+    {
+      auth_index: 0,
+      user_table: 'users',
+      username_column: 'username',
+      password_column: 'password',
+      database: {
+        adapter: 'mysql2',
+        database: 'casserver',
+        username: 'root',
+        password: 'password',
+        host: 'localhost'
+      }
+    }
+  end
+  let(:connection) { double('Connection', run_callbacks: nil) }
+  let(:connection_pool) { double('ConnectionPool',
+                                 connections: [connection],
+                                 checkin: nil) }
+
+  before do
+    load_server('default_config') if $LOG.nil? # ensure logger is present
+    ActiveRecord::Base.stub(:establish_connection)
+    ActiveRecord::Base.stub(:connection).and_return(connection)
+    ActiveRecord::Base.stub(:connection_pool).and_return(connection_pool)
+    CASServer::Authenticators::SQL.setup(options)
+  end
+
+  describe '#validate' do
+    let(:auth) { CASServer::Authenticators::SQL.new }
+    let(:username) { 'dave' }
+    let(:password) { 'secret' }
+    let(:user_model) { CASServer::Authenticators::SQL.user_models[0] }
+
+    before do
+      auth.configure(HashWithIndifferentAccess.new(options))
+    end
+
+    context 'when credentials match a user in the database' do
+      it 'returns true' do
+        conditions = ['username = ? AND password = ?', username, password]
+        user_model.should_receive(:find).with(:all, conditions: conditions)
+          .and_return([:user])
+        credentials = {
+          username: username,
+          password: password
+        }
+        expect(auth.validate(credentials)).to be true
+      end
+    end
+
+    context 'when credentials do not match a user in the database' do
+      it 'returns false' do
+        conditions = ['username = ? AND password = ?', username, password]
+        user_model.should_receive(:find).with(:all, conditions: conditions)
+          .and_return([])
+        credentials = {
+          username: username,
+          password: password
+        }
+        expect(auth.validate(credentials)).to be false
+      end
+    end
+
+    context 'when many SQL authenticators have been setup' do
+      let(:alt_options) do
+        {
+          auth_index: 1,
+          user_table: 'users',
+          username_column: 'username',
+          password_column: 'password',
+          database: {
+            adapter: 'mysql2',
+            database: 'casserver',
+            username: 'root',
+            password: 'password',
+            host: 'localhost'
+          }
+        }
+      end
+
+      before do
+        CASServer::Authenticators::SQL.setup(alt_options)
+      end
+
+      it 'chooses the correct user model based upon auth_index' do
+        # Original authenticator
+        conditions = ['username = ? AND password = ?', username, password]
+        user_model.should_receive(:find).with(:all, conditions: conditions)
+          .and_return([:user])
+        credentials = {
+          username: username,
+          password: password
+        }
+        expect(auth.validate(credentials)).to be true
+
+        # Alternate authenticator, different credentials, different user model
+        alt_auth = CASServer::Authenticators::SQL.new
+        alt_user_model = CASServer::Authenticators::SQL.user_models[1]
+        alt_username = 'dan'
+        conditions = ['username = ? AND password = ?', alt_username, password]
+        alt_user_model.should_receive(:find).with(:all, conditions: conditions)
+          .and_return([:user])
+        alt_credentials = {
+          username: alt_username,
+          password: password
+        }
+        alt_auth.configure(HashWithIndifferentAccess.new(alt_options))
+        expect(alt_auth.validate(alt_credentials)).to be true
+      end
+    end
+  end
+end