diff --git a/lib/bundler.rb b/lib/bundler.rb
index 3b494a6cdf1..df345539c8c 100644
--- a/lib/bundler.rb
+++ b/lib/bundler.rb
@@ -50,7 +50,6 @@ module Bundler
   autoload :FeatureFlag,            File.expand_path("bundler/feature_flag", __dir__)
   autoload :GemHelper,              File.expand_path("bundler/gem_helper", __dir__)
   autoload :GemHelpers,             File.expand_path("bundler/gem_helpers", __dir__)
-  autoload :GemRemoteFetcher,       File.expand_path("bundler/gem_remote_fetcher", __dir__)
   autoload :GemVersionPromoter,     File.expand_path("bundler/gem_version_promoter", __dir__)
   autoload :Graph,                  File.expand_path("bundler/graph", __dir__)
   autoload :Index,                  File.expand_path("bundler/index", __dir__)
diff --git a/lib/bundler/gem_remote_fetcher.rb b/lib/bundler/gem_remote_fetcher.rb
deleted file mode 100644
index 9577535d63c..00000000000
--- a/lib/bundler/gem_remote_fetcher.rb
+++ /dev/null
@@ -1,43 +0,0 @@
-# frozen_string_literal: true
-
-require "rubygems/remote_fetcher"
-
-module Bundler
-  # Adds support for setting custom HTTP headers when fetching gems from the
-  # server.
-  #
-  # TODO: Get rid of this when and if gemstash only supports RubyGems versions
-  # that contain https://github.com/rubygems/rubygems/commit/3db265cc20b2f813.
-  class GemRemoteFetcher < Gem::RemoteFetcher
-    attr_accessor :headers
-
-    # Extracted from RubyGems 2.4.
-    def fetch_http(uri, last_modified = nil, head = false, depth = 0)
-      fetch_type = head ? Net::HTTP::Head : Net::HTTP::Get
-      # beginning of change
-      response   = request uri, fetch_type, last_modified do |req|
-        headers.each {|k, v| req.add_field(k, v) } if headers
-      end
-      # end of change
-
-      case response
-      when Net::HTTPOK, Net::HTTPNotModified then
-        response.uri = uri if response.respond_to? :uri
-        head ? response : response.body
-      when Net::HTTPMovedPermanently, Net::HTTPFound, Net::HTTPSeeOther,
-           Net::HTTPTemporaryRedirect then
-        raise FetchError.new("too many redirects", uri) if depth > 10
-
-        location = URI.parse response["Location"]
-
-        if https?(uri) && !https?(location)
-          raise FetchError.new("redirecting to non-https resource: #{location}", uri)
-        end
-
-        fetch_http(location, last_modified, head, depth + 1)
-      else
-        raise FetchError.new("bad response #{response.message} #{response.code}", uri)
-      end
-    end
-  end
-end
diff --git a/lib/bundler/rubygems_integration.rb b/lib/bundler/rubygems_integration.rb
index 9b23a5c4c84..3ca1831deee 100644
--- a/lib/bundler/rubygems_integration.rb
+++ b/lib/bundler/rubygems_integration.rb
@@ -247,12 +247,6 @@ def ext_lock
       EXT_LOCK
     end
 
-    def fetch_prerelease_specs
-      fetch_specs(false, true)
-    rescue Gem::RemoteFetcher::FetchError
-      {} # if we can't download them, there aren't any
-    end
-
     def with_build_args(args)
       ext_lock.synchronize do
         old_args = build_args
@@ -502,8 +496,8 @@ def stub_rubygems(specs)
       end
     end
 
-    def fetch_specs(source, remote, name)
-      path = source + "#{name}.#{Gem.marshal_version}.gz"
+    def fetch_specs(remote, name)
+      path = remote.uri.to_s + "#{name}.#{Gem.marshal_version}.gz"
       fetcher = gem_remote_fetcher
       fetcher.headers = { "X-Gemfile-Source" => remote.original_uri.to_s } if remote.original_uri
       string = fetcher.fetch_path(path)
@@ -514,10 +508,8 @@ def fetch_specs(source, remote, name)
     end
 
     def fetch_all_remote_specs(remote)
-      source = remote.uri.is_a?(URI) ? remote.uri : URI.parse(source.to_s)
-
-      specs = fetch_specs(source, remote, "specs")
-      pres = fetch_specs(source, remote, "prerelease_specs") || []
+      specs = fetch_specs(remote, "specs")
+      pres = fetch_specs(remote, "prerelease_specs") || []
 
       specs.concat(pres)
     end
@@ -535,7 +527,7 @@ def gem_remote_fetcher
       require "resolv"
       proxy = configuration[:http_proxy]
       dns = Resolv::DNS.new
-      Bundler::GemRemoteFetcher.new(proxy, dns)
+      Gem::RemoteFetcher.new(proxy, dns)
     end
 
     def gem_from_path(path, policy = nil)
diff --git a/spec/bundler/rubygems_integration_spec.rb b/spec/bundler/rubygems_integration_spec.rb
index 26cbaa630b2..ce2b1000884 100644
--- a/spec/bundler/rubygems_integration_spec.rb
+++ b/spec/bundler/rubygems_integration_spec.rb
@@ -67,7 +67,7 @@
   end
 
   describe "#fetch_all_remote_specs" do
-    let(:uri) { URI("https://example.com") }
+    let(:uri) { "https://example.com" }
     let(:fetcher) { double("gem_remote_fetcher") }
     let(:specs_response) { Marshal.dump(["specs"]) }
     let(:prerelease_specs_response) { Marshal.dump(["prerelease_specs"]) }