diff --git a/Library/Homebrew/utils/pypi.rb b/Library/Homebrew/utils/pypi.rb
index 54ff4fd551..6b9189b422 100644
--- a/Library/Homebrew/utils/pypi.rb
+++ b/Library/Homebrew/utils/pypi.rb
@@ -307,6 +307,7 @@ module PyPI
     found_packages.sort.each do |package|
       if exclude_packages.include? package
         ohai "Excluding \"#{package}\"" if show_info
+        exclude_packages.delete package
         next
       end
 
@@ -332,6 +333,10 @@ module PyPI
       EOS
     end
 
+    unless exclude_packages.empty?
+      odie "Excluded superfluous packages: #{", ".join(exclude_packages)}"
+    end
+
     if print_only
       puts new_resource_blocks.chomp
       return