diff --git a/lib/arel.rb b/lib/arel.rb
index 6d7aec64b1..b27da2fb05 100644
--- a/lib/arel.rb
+++ b/lib/arel.rb
@@ -12,6 +12,8 @@ require 'arel/attributes'
 require 'arel/compatibility/wheres'
 
 #### these are deprecated
+# The Arel::Relation constant is referenced in Rails
+require 'arel/relation'
 require 'arel/expression'
 ####
 
diff --git a/lib/arel/relation.rb b/lib/arel/relation.rb
new file mode 100644
index 0000000000..87786d7701
--- /dev/null
+++ b/lib/arel/relation.rb
@@ -0,0 +1,6 @@
+module Arel
+  ###
+  # This is deprecated.  Fix rails, then remove this.
+  module Relation
+  end
+end
diff --git a/lib/arel/tree_manager.rb b/lib/arel/tree_manager.rb
index 21a52d8a60..99a7164e2e 100644
--- a/lib/arel/tree_manager.rb
+++ b/lib/arel/tree_manager.rb
@@ -1,5 +1,7 @@
 module Arel
   class TreeManager
+    # FIXME: Remove this.
+    include Arel::Relation
     include Arel::FactoryMethods
 
     attr_reader :ast, :engine