diff --git a/lib/active_record/session_store.rb b/lib/active_record/session_store.rb
index 4f56c5e..d1a7802 100644
--- a/lib/active_record/session_store.rb
+++ b/lib/active_record/session_store.rb
@@ -1,6 +1,7 @@
 require 'active_record'
 require 'active_record/session_store/version'
 require 'action_dispatch/session/active_record_store'
+require 'active_support'
 require 'active_support/core_ext/hash/keys'
 require 'json'
 
@@ -8,6 +9,12 @@ module ActiveRecord
   module SessionStore
     autoload :Session, 'active_record/session_store/session'
 
+    class << self
+      def deprecator
+        @deprecator ||= ActiveSupport::Deprecation.new("3.0", "ActiveRecord::SessionStore")
+      end
+    end
+
     module ClassMethods # :nodoc:
       mattr_accessor :serializer
 
diff --git a/lib/active_record/session_store/railtie.rb b/lib/active_record/session_store/railtie.rb
index 9159cb5..f2b867c 100644
--- a/lib/active_record/session_store/railtie.rb
+++ b/lib/active_record/session_store/railtie.rb
@@ -4,6 +4,10 @@ module ActiveRecord
   module SessionStore
     class Railtie < Rails::Railtie
       rake_tasks { load File.expand_path("../../../tasks/database.rake", __FILE__) }
+
+      initializer "activerecord-session_store.deprecator" do |app|
+        app.deprecators[:"activerecord-session_store"] = SessionStore.deprecator
+      end
     end
   end
 end
diff --git a/lib/active_record/session_store/session.rb b/lib/active_record/session_store/session.rb
index aec3253..3745766 100644
--- a/lib/active_record/session_store/session.rb
+++ b/lib/active_record/session_store/session.rb
@@ -38,6 +38,10 @@ def setup_sessid_compatibility!
             # Reset column info since it may be stale.
             reset_column_information
             if columns_hash['sessid']
+              SessionStore.deprecator.warn <<~MSG
+                Using a session ID column other than `session_id` is deprecated without replacement. You should migrate your session table to use `session_id`.
+              MSG
+
               def self.find_by_session_id(session_id)
                 find_by_sessid(session_id)
               end
diff --git a/test/helper.rb b/test/helper.rb
index 4a9ad7c..f51414d 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -7,6 +7,8 @@
 
 require 'active_record/session_store'
 
+ActiveRecord::SessionStore.deprecator.behavior = :raise
+
 ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
 
 SharedTestRoutes = ActionDispatch::Routing::RouteSet.new
diff --git a/test/session_test.rb b/test/session_test.rb
index e49c76d..8609bd4 100644
--- a/test/session_test.rb
+++ b/test/session_test.rb
@@ -100,7 +100,9 @@ def self.session_id_column
         session.sessid = "100"
         session.save!
 
-        found = klass.find_by_session_id("100")
+        found = assert_deprecated(ActiveRecord::SessionStore.deprecator) do
+          klass.find_by_session_id("100")
+        end
         assert_equal session, found
         assert_equal session.sessid, found.session_id
       ensure