diff --git a/Library/Contributions/cmd/brew-test-bot.rb b/Library/Contributions/cmd/brew-test-bot.rb
index 6ef014a60f01d40225e4a29c07cd76bb47a38a42..e8e40c44547b1720790117a702e580753b565242 100755
--- a/Library/Contributions/cmd/brew-test-bot.rb
+++ b/Library/Contributions/cmd/brew-test-bot.rb
@@ -326,9 +326,9 @@ class Test
 
     installed_gcc = false
     begin
-      deps = formula_object.stable.deps
+      deps = formula_object.stable.deps.to_a
       if formula_object.devel && !ARGV.include?('--HEAD')
-        deps += formula_object.devel.deps
+        deps |= formula_object.devel.deps.to_a
       end
       deps.each {|f| CompilerSelector.new(f.to_formula).compiler }