diff --git a/Library/Homebrew/cmd/test-bot.rb b/Library/Homebrew/cmd/test-bot.rb
index 5b73be2b71..c9a968ef6b 100644
--- a/Library/Homebrew/cmd/test-bot.rb
+++ b/Library/Homebrew/cmd/test-bot.rb
@@ -247,6 +247,7 @@ module Homebrew
     def safe_formula_canonical_name(formula_name)
       Formulary.factory(formula_name).full_name
     rescue TapFormulaUnavailableError => e
+      raise if e.tap.installed?
       test "brew", "tap", e.tap.name
       retry unless steps.last.failed?
     rescue FormulaUnavailableError, TapFormulaAmbiguityError, TapFormulaWithOldnameAmbiguityError