diff --git a/Library/Homebrew/cmd/doctor.rb b/Library/Homebrew/cmd/doctor.rb
index 1940ff2727..33e01f0fcc 100644
--- a/Library/Homebrew/cmd/doctor.rb
+++ b/Library/Homebrew/cmd/doctor.rb
@@ -32,7 +32,12 @@ end
 
 
 def path_folders
-  ENV['PATH'].split(':').collect{|p| remove_trailing_slash(File.expand_path(p))}.uniq
+  @path_folders ||= ENV['PATH'].split(':').collect do |p|
+    begin remove_trailing_slash(File.expand_path(p))
+    rescue ArgumentError
+      onoe "The following PATH component is invalid: #{p}"
+    end
+  end.uniq.compact
 end