diff --git a/Library/Homebrew/install.rb b/Library/Homebrew/install.rb
index b4ead5a279..4662779309 100755
--- a/Library/Homebrew/install.rb
+++ b/Library/Homebrew/install.rb
@@ -85,6 +85,7 @@ def install f
           puts "to copy the diff to the clipboard."
         end
 
+        ENV['HOMEBREW_DEBUG_PREFIX'] = f.prefix
         ENV['HOMEBREW_DEBUG_INSTALL'] = f.name
         interactive_shell
         nil