diff --git a/britney.py b/britney.py
index 43c1be8..40f808a 100755
--- a/britney.py
+++ b/britney.py
@@ -216,7 +216,7 @@ from britney_util import (old_libraries_format, same_source, undo_changes,
                           register_reverses, compute_reverse_tree,
                           read_nuninst, write_nuninst, write_heidi,
                           eval_uninst, newly_uninst, make_migrationitem,
-                          write_excuses)
+                          write_excuses, write_heidi_delta)
 from consts import (VERSION, SECTION, BINARIES, MAINTAINER, FAKESRC,
                    SOURCE, SOURCEVER, ARCHITECTURE, DEPENDS, CONFLICTS,
                    PROVIDES, RDEPENDS, RCONFLICTS, MULTIARCH, ESSENTIAL)
@@ -257,6 +257,8 @@ class Britney(object):
         apt_pkg.init()
         self.sources = {}
         self.binaries = {}
+        self.all_selected = []
+
         try:
             self.hints = self.read_hints(self.options.hintsdir)
         except AttributeError:
@@ -385,6 +387,9 @@ class Britney(object):
                  not getattr(self.options, k.lower()):
                 setattr(self.options, k.lower(), v)
 
+        if not hasattr(self.options, "heidi_delta_output"):
+            self.options.heidi_delta_output = self.options.heidi_output + "Delta"
+
         # Sort the architecture list
         allarches = sorted(self.options.architectures.split())
         arches = [x for x in allarches if x in self.options.nobreakall_arches.split()]
@@ -2272,6 +2277,7 @@ class Britney(object):
                                               newly_uninst(nuninst_start, nuninst_end)) + "\n")
             self.output_write("SUCCESS (%d/%d)\n" % (len(actions or self.upgrade_me), len(extra)))
             self.nuninst_orig = nuninst_end
+            self.all_selected += selected
             if not actions:
                 if recurse:
                     self.upgrade_me = sorted(extra)
@@ -2401,6 +2407,11 @@ class Britney(object):
             write_heidi(self.options.heidi_output, self.sources["testing"],
                         self.binaries["testing"])
 
+            self.__log("Writing delta to %s" % self.options.heidi_delta_output)
+            write_heidi_delta(self.options.heidi_delta_output,
+                              self.all_selected)
+
+
         self.printuninstchange()
         self.__log("Test completed!", type="I")
 
diff --git a/britney_util.py b/britney_util.py
index cfd2fa9..b23f7cf 100644
--- a/britney_util.py
+++ b/britney_util.py
@@ -407,6 +407,34 @@ def write_heidi(filename, sources_t, packages_t,
             srcsec = src[SECTION] or 'unknown'
             f.write('%s %s source %s\n' % (src_name, srcv, srcsec))
 
+
+def write_heidi_delta(filename, all_selected):
+    """Write the output delta
+
+    This method writes the packages to be upgraded, in the form:
+    <src-name> <src-version>
+    or (if the source is to be removed):
+    -<src-name> <src-version>
+
+    The order corresponds to that shown in update_output.
+    """
+    with open(filename, "w") as fd:
+
+        fd.write("#HeidiDelta\n")
+
+        for item in all_selected:
+            prefix = ""
+
+            if item.is_removal:
+                prefix = "-"
+
+            if item.architecture == 'source':
+                fd.write('%s%s %s\n' % (prefix, item.package, item.version))
+            else:
+                fd.write('%s%s %s %s\n' % (prefix, item.package,
+                                           item.version, item.architecture))
+
+
 def make_migrationitem(package, sources, VERSION=VERSION):
     """Convert a textual package specification to a MigrationItem