diff --git lib/rubygems.rb lib/rubygems.rb
index 246956bb14..0c698b2813 100644
--- lib/rubygems.rb
+++ lib/rubygems.rb
@@ -10,7 +10,7 @@
 require 'thread'
 
 module Gem
-  VERSION = '2.6.8'
+  VERSION = "2.6.10"
 end
 
 # Must be first since it unloads the prelude from 1.9.2
diff --git lib/rubygems/commands/setup_command.rb lib/rubygems/commands/setup_command.rb
index ebb08d24d7..2c29786224 100644
--- lib/rubygems/commands/setup_command.rb
+++ lib/rubygems/commands/setup_command.rb
@@ -47,7 +47,7 @@ def initialize
     end
 
     add_option '--[no-]document [TYPES]', Array,
-               'Generate documentation for RubyGems.',
+               'Generate documentation for RubyGems',
                'List the documentation types you wish to',
                'generate.  For example: rdoc,ri' do |value, options|
       options[:document] = case value
diff --git lib/rubygems/core_ext/kernel_require.rb lib/rubygems/core_ext/kernel_require.rb
index aa56ab5ec4..71a301c323 100755
--- lib/rubygems/core_ext/kernel_require.rb
+++ lib/rubygems/core_ext/kernel_require.rb
@@ -44,7 +44,7 @@ def require path
     spec = Gem.find_unresolved_default_spec(path)
     if spec
       Gem.remove_unresolved_default_spec(spec)
-      gem(spec.name)
+      Kernel.send(:gem, spec.name)
     end
 
     # If there are no unresolved deps, then we can use just try
diff --git lib/rubygems/ext/ext_conf_builder.rb lib/rubygems/ext/ext_conf_builder.rb
index 59e243b972..b6dde01950 100644
--- lib/rubygems/ext/ext_conf_builder.rb
+++ lib/rubygems/ext/ext_conf_builder.rb
@@ -48,9 +48,11 @@ def self.build(extension, directory, dest_path, results, args=[], lib_dir=nil)
           run cmd, results
         ensure
           if File.exist? 'mkmf.log'
-            results << "To see why this extension failed to compile, please check" \
-              " the mkmf.log which can be found here:\n"
-            results << "  " + File.join(dest_path, 'mkmf.log') + "\n"
+            unless $?.success? then
+              results << "To see why this extension failed to compile, please check" \
+                " the mkmf.log which can be found here:\n"
+              results << "  " + File.join(dest_path, 'mkmf.log') + "\n"
+            end
             FileUtils.mv 'mkmf.log', dest_path
           end
           siteconf.unlink
diff --git lib/rubygems/ext/rake_builder.rb lib/rubygems/ext/rake_builder.rb
index 682f1253e1..ec904e6c11 100644
--- lib/rubygems/ext/rake_builder.rb
+++ lib/rubygems/ext/rake_builder.rb
@@ -9,7 +9,7 @@ class Gem::Ext::RakeBuilder < Gem::Ext::Builder
 
   def self.build(extension, directory, dest_path, results, args=[], lib_dir=nil)
     if File.basename(extension) =~ /mkrf_conf/i then
-      cmd = "#{Gem.ruby} #{File.basename extension}"
+      cmd = "#{Gem.ruby} #{File.basename extension}".dup
       cmd << " #{args.join " "}" unless args.empty?
       run cmd, results
     end
diff --git lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb
index 40136eb894..139165102e 100644
--- lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb
+++ lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb
@@ -119,6 +119,7 @@ def to_dot
     #   {Vertex#successors}
     def ==(other)
       return false unless other
+      return true if equal?(other)
       vertices.each do |name, vertex|
         other_vertex = other.vertex_named(name)
         return false unless other_vertex
@@ -134,6 +135,7 @@ def ==(other)
     def add_child_vertex(name, payload, parent_names, requirement)
       root = !parent_names.delete(nil) { true }
       vertex = add_vertex(name, payload, root)
+      vertex.explicit_requirements << requirement if root
       parent_names.each do |parent_name|
         parent_node = vertex_named(parent_name)
         add_edge(parent_node, vertex, requirement)
@@ -152,7 +154,7 @@ def add_vertex(name, payload, root = false)
     # Detaches the {#vertex_named} `name` {Vertex} from the graph, recursively
     # removing any non-root vertices that were orphaned in the process
     # @param [String] name
-    # @return [void]
+    # @return [Array<Vertex>] the vertices which have been detached
     def detach_vertex_named(name)
       log.detach_vertex_named(self, name)
     end
diff --git lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph/detach_vertex_named.rb lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph/detach_vertex_named.rb
index 9ad34e8fe0..fa03e2d365 100644
--- lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph/detach_vertex_named.rb
+++ lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph/detach_vertex_named.rb
@@ -14,16 +14,23 @@ def self.action_name
 
       # (see Action#up)
       def up(graph)
-        return unless @vertex = graph.vertices.delete(name)
+        return [] unless @vertex = graph.vertices.delete(name)
+
+        removed_vertices = [@vertex]
         @vertex.outgoing_edges.each do |e|
           v = e.destination
           v.incoming_edges.delete(e)
-          graph.detach_vertex_named(v.name) unless v.root? || v.predecessors.any?
+          if !v.root? && v.incoming_edges.empty?
+            removed_vertices.concat graph.detach_vertex_named(v.name)
+          end
         end
+
         @vertex.incoming_edges.each do |e|
           v = e.origin
           v.outgoing_edges.delete(e)
         end
+
+        removed_vertices
       end
 
       # (see Action#down)
diff --git lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph/vertex.rb lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph/vertex.rb
index 88d109c94f..b5a0688a32 100644
--- lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph/vertex.rb
+++ lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph/vertex.rb
@@ -81,6 +81,7 @@ def inspect
       # @return [Boolean] whether the two vertices are equal, determined
       #   by a recursive traversal of each {Vertex#successors}
       def ==(other)
+        return true if equal?(other)
         shallow_eql?(other) &&
           successors.to_set == other.successors.to_set
       end
@@ -89,6 +90,7 @@ def ==(other)
       # @return [Boolean] whether the two vertices are equal, determined
       #   solely by {#name} and {#payload} equality
       def shallow_eql?(other)
+        return true if equal?(other)
         other &&
           name == other.name &&
           payload == other.payload
diff --git lib/rubygems/resolver/molinillo/lib/molinillo/gem_metadata.rb lib/rubygems/resolver/molinillo/lib/molinillo/gem_metadata.rb
index c50fa77bd5..dfddafe993 100644
--- lib/rubygems/resolver/molinillo/lib/molinillo/gem_metadata.rb
+++ lib/rubygems/resolver/molinillo/lib/molinillo/gem_metadata.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 module Gem::Resolver::Molinillo
   # The version of Gem::Resolver::Molinillo.
-  VERSION = '0.5.3'.freeze
+  VERSION = '0.5.5'.freeze
 end
diff --git lib/rubygems/resolver/molinillo/lib/molinillo/resolution.rb lib/rubygems/resolver/molinillo/lib/molinillo/resolution.rb
index 54a6c3fc17..ea497ddcaf 100644
--- lib/rubygems/resolver/molinillo/lib/molinillo/resolution.rb
+++ lib/rubygems/resolver/molinillo/lib/molinillo/resolution.rb
@@ -194,18 +194,20 @@ def unwind_for_conflict
       def state_index_for_unwind
         current_requirement = requirement
         existing_requirement = requirement_for_existing_name(name)
-        until current_requirement.nil?
-          current_state = find_state_for(current_requirement)
-          return states.index(current_state) if state_any?(current_state)
-          current_requirement = parent_of(current_requirement)
+        index = -1
+        [current_requirement, existing_requirement].each do |r|
+          until r.nil?
+            current_state = find_state_for(r)
+            if state_any?(current_state)
+              current_index = states.index(current_state)
+              index = current_index if current_index > index
+              break
+            end
+            r = parent_of(r)
+          end
         end
 
-        until existing_requirement.nil?
-          existing_state = find_state_for(existing_requirement)
-          return states.index(existing_state) if state_any?(existing_state)
-          existing_requirement = parent_of(existing_requirement)
-        end
-        -1
+        index
       end
 
       # @return [Object] the requirement that led to `requirement` being added
@@ -364,19 +366,17 @@ def fixup_swapped_children(vertex)
           if matching_deps.empty? && !succ.root? && succ.predecessors.to_a == [vertex]
             debug(depth) { "Removing orphaned spec #{succ.name} after swapping #{name}" }
             succ.requirements.each { |r| @parent_of.delete(r) }
-            activated.detach_vertex_named(succ.name)
 
-            all_successor_names = succ.recursive_successors.map(&:name)
-
-            requirements.delete_if do |requirement|
-              requirement_name = name_for(requirement)
-              (requirement_name == succ.name) || all_successor_names.include?(requirement_name)
+            removed_names = activated.detach_vertex_named(succ.name).map(&:name)
+            requirements.delete_if do |r|
+              # the only removed vertices are those with no other requirements,
+              # so it's safe to delete only based upon name here
+              removed_names.include?(name_for(r))
             end
           elsif !matching_deps.include?(outgoing_edge.requirement)
             activated.delete_edge(outgoing_edge)
             requirements.delete(outgoing_edge.requirement)
           end
-          matching_deps.delete(outgoing_edge.requirement)
         end
       end
 
diff --git lib/rubygems/server.rb lib/rubygems/server.rb
index 63dfe31b35..81df0e608e 100644
--- lib/rubygems/server.rb
+++ lib/rubygems/server.rb
@@ -2,6 +2,7 @@
 require 'webrick'
 require 'zlib'
 require 'erb'
+require 'uri'
 
 require 'rubygems'
 require 'rubygems/rdoc'
@@ -68,7 +69,7 @@ class Gem::Server
         <h1>Summary</h1>
   <p>There are <%=values["gem_count"]%> gems installed:</p>
   <p>
-  <%= values["specs"].map { |v| "<a href\"##{u v["name"]}\">#{h v["name"]}</a>" }.join ', ' %>.
+  <%= values["specs"].map { |v| "<a href=\"##{u v["name"]}\">#{h v["name"]}</a>" }.join ', ' %>.
   <h1>Gems</h1>
 
   <dl>
@@ -81,20 +82,20 @@ class Gem::Server
     <b><%=h spec["name"]%> <%=h spec["version"]%></b>
 
     <% if spec["ri_installed"] || spec["rdoc_installed"] then %>
-      <a href="<%=u spec["doc_path"]%>">[rdoc]</a>
+      <a href="<%=spec["doc_path"]%>">[rdoc]</a>
     <% else %>
       <span title="rdoc not installed">[rdoc]</span>
     <% end %>
 
     <% if spec["homepage"] then %>
-      <a href="<%=u spec["homepage"]%>" title="<%=h spec["homepage"]%>">[www]</a>
+      <a href="<%=uri_encode spec["homepage"]%>" title="<%=h spec["homepage"]%>">[www]</a>
     <% else %>
       <span title="no homepage available">[www]</span>
     <% end %>
 
     <% if spec["has_deps"] then %>
      - depends on
-      <%= spec["dependencies"].map { |v| "<a href=\"##{u v["name"]}>#{h v["name"]}</a>" }.join ', ' %>.
+      <%= spec["dependencies"].map { |v| "<a href=\"##{u v["name"]}\">#{h v["name"]}</a>" }.join ', ' %>.
     <% end %>
     </dt>
     <dd>
@@ -455,6 +456,12 @@ def add_date res
     end.max
   end
 
+  def uri_encode(str)
+    str.gsub(URI::UNSAFE) do |match|
+      match.each_byte.map { |c| sprintf('%%%02X', c.ord) }.join
+    end
+  end
+
   def doc_root gem_name
     if have_rdoc_4_plus? then
       "/doc_root/#{u gem_name}/"
diff --git lib/rubygems/stub_specification.rb lib/rubygems/stub_specification.rb
index 1c56a102c5..b741843124 100644
--- lib/rubygems/stub_specification.rb
+++ lib/rubygems/stub_specification.rb
@@ -39,7 +39,12 @@ class StubLine # :nodoc: all
     def initialize data, extensions
       parts          = data[PREFIX.length..-1].split(" ".freeze, 4)
       @name          = parts[0].freeze
-      @version       = Gem::Version.new parts[1]
+      @version       = if Gem::Version.correct?(parts[1])
+                         Gem::Version.new(parts[1])
+                       else
+                         Gem::Version.new(0)
+                       end
+
       @platform      = Gem::Platform.new parts[2]
       @extensions    = extensions
       @full_name     = if platform == Gem::Platform::RUBY
diff --git lib/rubygems/version.rb lib/rubygems/version.rb
index 2f6cfae6ed..17dd7b0795 100644
--- lib/rubygems/version.rb
+++ lib/rubygems/version.rb
@@ -204,8 +204,12 @@ def self.new version # :nodoc:
   # series of digits or ASCII letters separated by dots.
 
   def initialize version
-    raise ArgumentError, "Malformed version number string #{version}" unless
-      self.class.correct?(version)
+    unless self.class.correct?(version)
+      raise ArgumentError, "Malformed version number string #{version}"
+    end
+
+    # If version is an empty string convert it to 0
+    version = 0 if version =~ /\A\s*\Z/
 
     @version = version.to_s.strip.gsub("-",".pre.")
     @segments = nil
diff --git test/rubygems/test_gem.rb test/rubygems/test_gem.rb
index 787350727f..e1ebebffb5 100644
--- test/rubygems/test_gem.rb
+++ test/rubygems/test_gem.rb
@@ -1451,6 +1451,7 @@ def test_looks_for_gemdeps_files_automatically_on_start
     ENV['RUBYGEMS_GEMDEPS'] = "-"
 
     out = `#{Gem.ruby.dup.untaint} -I "#{LIB_PATH.untaint}" -rubygems -e "p Gem.loaded_specs.values.map(&:full_name).sort"`
+    out.sub!(/, "openssl-#{Gem::Version::VERSION_PATTERN}"/, "")
 
     assert_equal '["a-1", "b-1", "c-1"]', out.strip
   end
@@ -1484,6 +1485,7 @@ def test_looks_for_gemdeps_files_automatically_on_start_in_parent_dir
     out = Dir.chdir "sub1" do
       `#{Gem.ruby.dup.untaint} -I "#{LIB_PATH.untaint}" -rubygems -e "p Gem.loaded_specs.values.map(&:full_name).sort"`
     end
+    out.sub!(/, "openssl-#{Gem::Version::VERSION_PATTERN}"/, "")
 
     Dir.rmdir "sub1"
 
diff --git test/rubygems/test_gem_ext_ext_conf_builder.rb test/rubygems/test_gem_ext_ext_conf_builder.rb
index f5d10fae50..b43ebf00d9 100644
--- test/rubygems/test_gem_ext_ext_conf_builder.rb
+++ test/rubygems/test_gem_ext_ext_conf_builder.rb
@@ -111,6 +111,29 @@ def test_class_build_extconf_fail
 
     assert_match(/^#{Gem.ruby}.* extconf.rb/, output[1])
     assert_match(File.join(@dest_path, 'mkmf.log'), output[4])
+    assert_includes(output, "To see why this extension failed to compile, please check the mkmf.log which can be found here:\n")
+
+    assert_path_exists File.join @dest_path, 'mkmf.log'
+  end
+
+  def test_class_build_extconf_success_without_warning
+    if vc_windows? && !nmake_found?
+      skip("test_class_build_extconf_fail skipped - nmake not found")
+    end
+
+    File.open File.join(@ext, 'extconf.rb'), 'w' do |extconf|
+      extconf.puts "require 'mkmf'"
+      extconf.puts "File.open('mkmf.log', 'w'){|f| f.write('a')}"
+      extconf.puts "create_makefile 'foo'"
+    end
+
+    output = []
+
+    Dir.chdir @ext do
+      Gem::Ext::ExtConfBuilder.build 'extconf.rb', nil, @dest_path, output
+    end
+
+    refute_includes(output, "To see why this extension failed to compile, please check the mkmf.log which can be found here:\n")
 
     assert_path_exists File.join @dest_path, 'mkmf.log'
   end
diff --git test/rubygems/test_gem_ext_rake_builder.rb test/rubygems/test_gem_ext_rake_builder.rb
index b728f8f30a..9f59f51660 100644
--- test/rubygems/test_gem_ext_rake_builder.rb
+++ test/rubygems/test_gem_ext_rake_builder.rb
@@ -14,14 +14,7 @@ def setup
   end
 
   def test_class_build
-    File.open File.join(@ext, 'mkrf_conf.rb'), 'w' do |mkrf_conf|
-      mkrf_conf.puts <<-EO_MKRF
-        File.open("Rakefile","w") do |f|
-          f.puts "task :default"
-        end
-      EO_MKRF
-    end
-
+    create_temp_mkrf_file('task :default')
     output = []
     realdir = nil # HACK /tmp vs. /private/tmp
 
@@ -39,15 +32,31 @@ def test_class_build
     end
   end
 
+  # https://github.com/rubygems/rubygems/pull/1819
+  #
+  # It should not fail with a non-empty args list either
+  def test_class_build_with_args
+    create_temp_mkrf_file('task :default')
+    output = []
+    realdir = nil # HACK /tmp vs. /private/tmp
+
+    build_rake_in do |rake|
+      Dir.chdir @ext do
+        realdir = Dir.pwd
+        non_empty_args_list = ['']
+        Gem::Ext::RakeBuilder.build 'mkrf_conf.rb', nil, @dest_path, output, non_empty_args_list
+      end
+
+      output = output.join "\n"
+
+      refute_match %r%^rake failed:%, output
+      assert_match %r%^#{Regexp.escape @@ruby} mkrf_conf\.rb%, output
+      assert_match %r%^#{Regexp.escape rake} RUBYARCHDIR=#{Regexp.escape @dest_path} RUBYLIBDIR=#{Regexp.escape @dest_path}%, output
+    end
+  end  
+
   def test_class_build_fail
-    File.open File.join(@ext, 'mkrf_conf.rb'), 'w' do |mkrf_conf|
-      mkrf_conf.puts <<-EO_MKRF
-        File.open("Rakefile","w") do |f|
-          f.puts "task :default do abort 'fail' end"
-        end
-      EO_MKRF
-    end
-
+    create_temp_mkrf_file("task :default do abort 'fail' end")
     output = []
 
     build_rake_in(false) do |rake|
@@ -60,6 +69,14 @@ def test_class_build_fail
       assert_match %r%^rake failed%, error.message
     end
   end
-
+  
+  def create_temp_mkrf_file(rakefile_content)
+    File.open File.join(@ext, 'mkrf_conf.rb'), 'w' do |mkrf_conf|
+      mkrf_conf.puts <<-EO_MKRF
+        File.open("Rakefile","w") do |f|
+          f.puts "#{rakefile_content}"
+        end
+      EO_MKRF
+    end
+  end
 end
-
diff --git test/rubygems/test_gem_remote_fetcher.rb test/rubygems/test_gem_remote_fetcher.rb
index ca62a8342e..cb994462cd 100644
--- test/rubygems/test_gem_remote_fetcher.rb
+++ test/rubygems/test_gem_remote_fetcher.rb
@@ -163,7 +163,7 @@ def test_fetch_size_socket_error
     fetcher = Gem::RemoteFetcher.new nil
     @fetcher = fetcher
     def fetcher.request(uri, request_class, last_modified = nil)
-      raise SocketError, "tarded"
+      raise SocketError, "oops"
     end
 
     uri = 'http://gems.example.com/yaml'
@@ -171,7 +171,7 @@ def fetcher.request(uri, request_class, last_modified = nil)
       fetcher.fetch_size uri
     end
 
-    assert_equal "SocketError: tarded (#{uri})", e.message
+    assert_equal "SocketError: oops (#{uri})", e.message
   end
 
   def test_no_proxy
diff --git test/rubygems/test_gem_server.rb test/rubygems/test_gem_server.rb
index 0ece6d67ef..4873fac5b6 100644
--- test/rubygems/test_gem_server.rb
+++ test/rubygems/test_gem_server.rb
@@ -392,6 +392,22 @@ def test_specs_gz
                  Marshal.load(Gem.gunzip(@res.body))
   end
 
+  def test_uri_encode
+    url_safe = @server.uri_encode 'http://rubyonrails.org/">malicious_content</a>'
+    assert_equal url_safe, 'http://rubyonrails.org/%22%3Emalicious_content%3C/a%3E'
+  end
+
+  # Regression test for issue #1793: incorrect URL encoding.
+  # Checking that no URLs have had '://' incorrectly encoded
+  def test_regression_1793
+    data = StringIO.new "GET / HTTP/1.0\r\n\r\n"
+    @req.parse data
+
+    @server.root @req, @res
+
+    refute_match %r|%3A%2F%2F|, @res.body
+  end
+
   def util_listen
     webrick = Object.new
     webrick.instance_variable_set :@listeners, []
diff --git test/rubygems/test_gem_specification.rb test/rubygems/test_gem_specification.rb
index 2c0ea770b5..d43289d745 100644
--- test/rubygems/test_gem_specification.rb
+++ test/rubygems/test_gem_specification.rb
@@ -1260,7 +1260,7 @@ def test_initialize_copy_broken
       s.version = '1'
     end
 
-    spec.instance_variable_set :@licenses, Object.new.singleton_class
+    spec.instance_variable_set :@licenses, (class << (Object.new);self;end)
     spec.loaded_from = '/path/to/file'
 
     e = assert_raises Gem::FormatException do
diff --git test/rubygems/test_gem_stub_specification.rb test/rubygems/test_gem_stub_specification.rb
index 4cba13e139..5316449fba 100644
--- test/rubygems/test_gem_stub_specification.rb
+++ test/rubygems/test_gem_stub_specification.rb
@@ -33,6 +33,20 @@ def test_initialize_extension
     assert_equal %w[ext/stub_e/extconf.rb],   stub.extensions
   end
 
+  def test_initialize_version
+    stub = stub_with_version
+
+    assert_equal 'stub_v',                    stub.name
+    assert_equal v(2),                        stub.version
+  end
+
+  def test_initialize_with_empty_version
+    stub = stub_without_version
+
+    assert_equal 'stub_v',                    stub.name
+    assert_equal v(0),                        stub.version
+  end
+
   def test_initialize_missing_stubline
     stub = Gem::StubSpecification.gemspec_stub(BAR, @base_dir, @gems_dir)
     assert_equal "bar", stub.name
@@ -164,6 +178,53 @@ def test_to_spec_missing_extensions
     assert stub.to_spec.instance_variable_get :@ignored
   end
 
+  def stub_with_version
+    spec = File.join @gemhome, 'specifications', 'stub_e-2.gemspec'
+    open spec, 'w' do |io|
+      io.write <<-STUB
+# -*- encoding: utf-8 -*-
+# stub: stub_v 2 ruby lib
+
+Gem::Specification.new do |s|
+  s.name = 'stub_v'
+  s.version = Gem::Version.new '2'
+end
+      STUB
+
+      io.flush
+
+      stub = Gem::StubSpecification.gemspec_stub io.path, @gemhome, File.join(@gemhome, 'gems')
+
+      yield stub if block_given?
+
+      return stub
+    end
+  end
+
+  def stub_without_version
+    spec = File.join @gemhome, 'specifications', 'stub-2.gemspec'
+    open spec, 'w' do |io|
+      io.write <<-STUB
+# -*- encoding: utf-8 -*-
+# stub: stub_v ruby lib
+
+Gem::Specification.new do |s|
+  s.name = 'stub_v'
+  s.version = ""
+end
+      STUB
+
+      io.flush
+
+      stub = Gem::StubSpecification.gemspec_stub io.path, @gemhome, File.join(@gemhome, 'gems')
+
+      yield stub if block_given?
+
+      return stub
+    end
+
+  end
+
   def stub_with_extension
     spec = File.join @gemhome, 'specifications', 'stub_e-2.gemspec'
     open spec, 'w' do |io|
diff --git test/rubygems/test_gem_version.rb test/rubygems/test_gem_version.rb
index 9898669ce6..1897d44905 100644
--- test/rubygems/test_gem_version.rb
+++ test/rubygems/test_gem_version.rb
@@ -91,6 +91,12 @@ def test_initialize_bad
     end
   end
 
+  def test_empty_version
+    ["", "   ", " "].each do |empty|
+      assert_equal "0", Gem::Version.new(empty).version
+    end
+  end
+
   def test_prerelease
     assert_prerelease "1.2.0.a"
     assert_prerelease "2.9.b"
diff --git test/rubygems/test_require.rb test/rubygems/test_require.rb
index 04cbc094d8..dd606e44d4 100644
--- test/rubygems/test_require.rb
+++ test/rubygems/test_require.rb
@@ -341,6 +341,31 @@ class << ::Gem
     Kernel::RUBYGEMS_ACTIVATION_MONITOR.exit
   end
 
+  def test_require_when_gem_defined
+    default_gem_spec = new_default_spec("default", "2.0.0.0",
+                                        nil, "default/gem.rb")
+    install_default_specs(default_gem_spec)
+    c = Class.new do
+      def self.gem(*args)
+        raise "received #gem with #{args.inspect}"
+      end
+    end
+    assert c.send(:require, "default/gem")
+    assert_equal %w(default-2.0.0.0), loaded_spec_names
+  end
+
+  def test_require_default_when_gem_defined
+    a = new_spec("a", "1", nil, "lib/a.rb")
+    install_specs a
+    c = Class.new do
+      def self.gem(*args)
+        raise "received #gem with #{args.inspect}"
+      end
+    end
+    assert c.send(:require, "a")
+    assert_equal %w(a-1), loaded_spec_names
+  end
+
   def silence_warnings
     old_verbose, $VERBOSE = $VERBOSE, false
     yield