diff --git a/spec/bundler/support/helpers.rb b/spec/bundler/support/helpers.rb
index 660a6817fe..b532fdc462 100644
--- a/spec/bundler/support/helpers.rb
+++ b/spec/bundler/support/helpers.rb
@@ -328,9 +328,14 @@ module Spec
           FileUtils.cp shipped_file, target_shipped_file, :preserve => true
         end
 
+        # for Ruby core repository
+        if File.exist? File.join(build_path, "lib/bundler/bundler.gemspec")
+          FileUtils.mv File.join(build_path, "lib/bundler/bundler.gemspec"), build_path
+        end
+
         replace_version_file(version, dir: build_path) # rubocop:disable Style/HashSyntax
 
-        gem_command! "build #{shipped_gemspec}", :dir => build_path
+        gem_command! "build bundler.gemspec", :dir => build_path
 
         yield(bundler_path)
       ensure
diff --git a/spec/bundler/support/path.rb b/spec/bundler/support/path.rb
index c64f555d90..b851fa389a 100644
--- a/spec/bundler/support/path.rb
+++ b/spec/bundler/support/path.rb
@@ -37,10 +37,6 @@ module Spec
       @tracked_files ||= sys_exec(ruby_core? ? "git ls-files -z -- lib/bundler lib/bundler.rb spec/bundler man/bundler*" : "git ls-files -z", :dir => root).split("\x0")
     end
 
-    def shipped_gemspec
-      @shipped_gemspec ||= ruby_core? ? "lib/bundler/bundler.gemspec" : "bundler.gemspec"
-    end
-
     def shipped_files
       @shipped_files ||= sys_exec(ruby_core? ? "git ls-files -z -- lib/bundler lib/bundler.rb man/bundler* libexec/bundle*" : "git ls-files -z -- lib man exe CHANGELOG.md LICENSE.md README.md bundler.gemspec", :dir => root).split("\x0")
     end