diff --git a/Library/Homebrew/dev-cmd/test.rb b/Library/Homebrew/dev-cmd/test.rb
index a03927cd48..042da3cbd1 100644
--- a/Library/Homebrew/dev-cmd/test.rb
+++ b/Library/Homebrew/dev-cmd/test.rb
@@ -119,6 +119,7 @@ module Homebrew
     if args.retry? && @test_failed.add?(f)
       oh1 "Testing #{f.full_name} (again)"
       f.clear_cache
+      ENV["RUST_BACKTRACE"] = "full"
       true
     else
       Homebrew.failed = true