diff --git a/Library/Contributions/cmd/brew-unpack.rb b/Library/Contributions/cmd/brew-unpack.rb
index c1ca264749..b5023f1a25 100755
--- a/Library/Contributions/cmd/brew-unpack.rb
+++ b/Library/Contributions/cmd/brew-unpack.rb
@@ -28,6 +28,7 @@ module UnpackPatch
     return unless ARGV.flag? "--patch"
 
     begin
+      # Silence complaints about re-setting constants.
       old_verbose = $VERBOSE
       $VERBOSE = nil
       Formula.const_set "DATA", ScriptDataReader.load(path)
@@ -35,6 +36,14 @@ module UnpackPatch
       $VERBOSE = old_verbose
     end
 
+    # Legacy patches are fixed by setting Formula::DATA.
+    # Now, handle instances of IOPatch.
+    patchlist.select{|p| p.is_a? IOPatch}.each do |patch|
+      if patch.instance_variable_get(:@io) == :DATA
+        patch.instance_variable_set :@io, ScriptDataReader.load(path)
+      end
+    end
+
     super
   end
 end