diff --git a/test/rubygems/test_project_sanity.rb b/test/rubygems/test_project_sanity.rb
index 7a7b779b08..8f23b2d8c0 100644
--- a/test/rubygems/test_project_sanity.rb
+++ b/test/rubygems/test_project_sanity.rb
@@ -12,25 +12,26 @@ class TestGemProjectSanity < Gem::TestCase
 
   def test_manifest_is_up_to_date
     pend unless File.exist?("#{root}/Rakefile")
+    rake = "#{root}/bin/rake"
 
-    _, status = Open3.capture2e("rake check_manifest")
+    _, status = Open3.capture2e(rake, "check_manifest")
 
     unless status.success?
       original_contents = File.read("#{root}/Manifest.txt")
 
       # Update the manifest to see if it fixes the problem
-      Open3.capture2e("rake update_manifest")
+      Open3.capture2e(rake, "update_manifest")
 
-      out, status = Open3.capture2e("rake check_manifest")
+      out, status = Open3.capture2e(rake, "check_manifest")
 
       # If `rake update_manifest` fixed the problem, that was the original
       # issue, otherwise it was an unknown error, so print the error output
       if status.success?
         File.write("#{root}/Manifest.txt", original_contents)
 
-        raise "Expected Manifest.txt to be up to date, but it's not. Run `rake update_manifest` to sync it."
+        raise "Expected Manifest.txt to be up to date, but it's not. Run `bin/rake update_manifest` to sync it."
       else
-        raise "There was an error running `rake check_manifest`: #{out}"
+        raise "There was an error running `bin/rake check_manifest`: #{out}"
       end
     end
   end