4 files changed, 16 insertions, 2 deletions
diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index ac42d9c630..bec1edf6c1 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Fix remove_constant to correctly handle constant names of the form "::A::...". References #6720. [Nicholas Seckar]
+
 * Fixed Array#to_xml when it contains a series of hashes (each piece would get its own XML declaration) #6610 [thkarcher/cyu]
 
 * Added Time#to_s(:time) which will just return H:M, like 17:44 [DHH]
diff --git a/activesupport/lib/active_support/dependencies.rb b/activesupport/lib/active_support/dependencies.rb
index ad4e4da669..b169393bf7 100644
--- a/activesupport/lib/active_support/dependencies.rb
+++ b/activesupport/lib/active_support/dependencies.rb
@@ -405,8 +405,9 @@ protected
   def remove_constant(const)
     return false unless qualified_const_defined? const
     
+    const = $1 if /\A::(.*)\Z/ =~ const.to_s
     names = const.split('::')
-    if names.size == 1 || names.first.empty? # It's under Object
+    if names.size == 1 # It's under Object
       parent = Object
     else
       parent = (names[0..-2] * '::').constantize
diff --git a/activesupport/test/core_ext/array_ext_test.rb b/activesupport/test/core_ext/array_ext_test.rb
index 709df84f06..87608de8d5 100644
--- a/activesupport/test/core_ext/array_ext_test.rb
+++ b/activesupport/test/core_ext/array_ext_test.rb
@@ -176,7 +176,7 @@ class ArrayToXmlTests < Test::Unit::TestCase
       { :name => "Jason", :age => 31, :age_in_millis => BigDecimal.new('1.0') }
     ].to_xml(:skip_instruct => false, :indent => 0)
 
-    assert /^<\?xml [^>]*/.match(xml)
+    assert(/^<\?xml [^>]*/.match(xml))
     assert xml.rindex(/<\?xml /) == 0
   end
 end
diff --git a/activesupport/test/dependencies_test.rb b/activesupport/test/dependencies_test.rb
index 954f2f4a85..52f83e0f9f 100644
--- a/activesupport/test/dependencies_test.rb
+++ b/activesupport/test/dependencies_test.rb
@@ -691,4 +691,15 @@ class DependenciesTest < Test::Unit::TestCase
   ensure
     Object.send(:remove_const, :RaisesNameError) if defined?(::RaisesNameError)
   end
+  
+  def test_remove_constant_handles_double_colon_at_start
+    Object.const_set 'DeleteMe', Module.new
+    DeleteMe.const_set 'OrMe', Module.new
+    Dependencies.send :remove_constant, "::DeleteMe::OrMe"
+    assert ! defined?(DeleteMe::OrMe)
+    assert defined?(DeleteMe)
+    Dependencies.send :remove_constant, "::DeleteMe"
+    assert ! defined?(DeleteMe)
+  end
+  
 end