diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index 40a1866428..3a7652f5bf 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -113,7 +113,7 @@ class Module
       raise ArgumentError, "Can only automatically set the delegation prefix when delegating to a method."
     end
 
-    prefix = options[:prefix] && "#{options[:prefix] == true ? to : options[:prefix]}_"
+    prefix = options[:prefix] && "#{options[:prefix] == true ? to : options[:prefix]}_" || ''
 
     file, line = caller.first.split(':', 2)
     line = line.to_i
diff --git a/activesupport/test/core_ext/module_test.rb b/activesupport/test/core_ext/module_test.rb
index 5d9cdf22c2..75404ec0e1 100644
--- a/activesupport/test/core_ext/module_test.rb
+++ b/activesupport/test/core_ext/module_test.rb
@@ -47,6 +47,14 @@ Project   = Struct.new(:description, :person) do
   delegate :to_f, :to => :description, :allow_nil => true
 end
 
+Developer = Struct.new(:client) do
+  delegate :name, :to => :client, :prefix => nil
+end
+
+Tester = Struct.new(:client) do
+  delegate :name, :to => :client, :prefix => false
+end
+
 class Name
   delegate :upcase, :to => :@full_name
 
@@ -97,6 +105,11 @@ class ModuleTest < Test::Unit::TestCase
     assert_equal invoice.customer_city, "Chicago"
   end
 
+  def test_delegation_prefix_with_nil_or_false
+    assert_equal Developer.new(@david).name, "David"
+    assert_equal Tester.new(@david).name, "David"
+  end
+
   def test_delegation_prefix_with_instance_variable
     assert_raise ArgumentError do
       Class.new do