diff --git a/Lib/distutils/command/sdist.py b/Lib/distutils/command/sdist.py
index f33406c..b2088f9 100644
--- a/Lib/distutils/command/sdist.py
+++ b/Lib/distutils/command/sdist.py
@@ -179,66 +179,34 @@
         distribution, and put it in 'self.filelist'.  This might involve
         reading the manifest template (and writing the manifest), or just
         reading the manifest, or just using the default file set -- it all
-        depends on the user's options and the state of the filesystem.
+        depends on the user's options.
         """
-        # If we have a manifest template, see if it's newer than the
-        # manifest; if so, we'll regenerate the manifest.
+        # new behavior:
+        # the file list is recalculated everytime because
+        # even if MANIFEST.in or setup.py are not changed
+        # the user might have added some files in the tree that
+        # need to be included.
+        #
+        #  This makes --force the default and only behavior.
         template_exists = os.path.isfile(self.template)
+        if not template_exists:
+            self.warn(("manifest template '%s' does not exist " +
+                        "(using default file list)") %
+                        self.template)
+        self.filelist.findall()
+
+        if self.use_defaults:
+            self.add_defaults()
+
         if template_exists:
-            template_newer = dep_util.newer(self.template, self.manifest)
+            self.read_template()
 
-        # The contents of the manifest file almost certainly depend on the
-        # setup script as well as the manifest template -- so if the setup
-        # script is newer than the manifest, we'll regenerate the manifest
-        # from the template.  (Well, not quite: if we already have a
-        # manifest, but there's no template -- which will happen if the
-        # developer elects to generate a manifest some other way -- then we
-        # can't regenerate the manifest, so we don't.)
-        self.debug_print("checking if %s newer than %s" %
-                         (self.distribution.script_name, self.manifest))
-        setup_newer = dep_util.newer(self.distribution.script_name,
-                                     self.manifest)
+        if self.prune:
+            self.prune_file_list()
 
-        # cases:
-        #   1) no manifest, template exists: generate manifest
-        #      (covered by 2a: no manifest == template newer)
-        #   2) manifest & template exist:
-        #      2a) template or setup script newer than manifest:
-        #          regenerate manifest
-        #      2b) manifest newer than both:
-        #          do nothing (unless --force or --manifest-only)
-        #   3) manifest exists, no template:
-        #      do nothing (unless --force or --manifest-only)
-        #   4) no manifest, no template: generate w/ warning ("defaults only")
-
-        manifest_outofdate = (template_exists and
-                              (template_newer or setup_newer))
-        force_regen = self.force_manifest or self.manifest_only
-        manifest_exists = os.path.isfile(self.manifest)
-        neither_exists = (not template_exists and not manifest_exists)
-
-        # Regenerate the manifest if necessary (or if explicitly told to)
-        if manifest_outofdate or neither_exists or force_regen:
-            if not template_exists:
-                self.warn("manifest template '%s' does not exist "
-                          "(using default file list)"
-                          % self.template)
-            self.filelist.findall()
-
-            if self.use_defaults:
-                self.add_defaults()
-            if template_exists:
-                self.read_template()
-            if self.prune:
-                self.prune_file_list()
-
-            self.filelist.sort()
-            self.filelist.remove_duplicates()
-            self.write_manifest()
-
-        # Don't regenerate the manifest, just read it in.
-        else:
-            self.read_manifest()
+        self.filelist.sort()
+        self.filelist.remove_duplicates()
+        self.write_manifest()
 
     def add_defaults(self):
         """Add all the default files to self.filelist:
diff --git a/Lib/distutils/tests/test_sdist.py b/Lib/distutils/tests/test_sdist.py
index e0f1e93..1bc36c5 100644
--- a/Lib/distutils/tests/test_sdist.py
+++ b/Lib/distutils/tests/test_sdist.py
@@ -346,6 +346,47 @@
         finally:
             archive.close()
 
+    def test_get_file_list(self):
+        # make sure MANIFEST is recalculated
+        dist, cmd = self.get_cmd()
+
+        # filling data_files by pointing files in package_data
+        dist.package_data = {'somecode': ['*.txt']}
+        self.write_file((self.tmp_dir, 'somecode', 'doc.txt'), '#')
+        cmd.ensure_finalized()
+        cmd.run()
+
+        f = open(cmd.manifest)
+        try:
+            manifest = [line.strip() for line in f.read().split('\n')
+                        if line.strip() != '']
+        finally:
+            f.close()
+
+        self.assertEquals(len(manifest), 4)
+
+        # adding a file
+        self.write_file((self.tmp_dir, 'somecode', 'doc2.txt'), '#')
+
+        # make sure build_py is reinitinialized, like a fresh run
+        build_py = dist.get_command_obj('build_py')
+        build_py.finalized = False
+        build_py.ensure_finalized()
+
+        cmd.run()
+
+        f = open(cmd.manifest)
+        try:
+            manifest2 = [line.strip() for line in f.read().split('\n')
+                         if line.strip() != '']
+        finally:
+            f.close()
+
+        # do we have the new file in MANIFEST ?
+        self.assertEquals(len(manifest2), 5)
+        self.assertIn('doc2.txt', manifest2[-1])
+
+
 def test_suite():
     return unittest.makeSuite(SDistTestCase)
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 6b38425..4f7ee6c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -366,6 +366,8 @@
 Library
 -------
 
+- Issue #8688: Distutils now recalculates MANIFEST everytime.
+
 - Issue #8477: ssl.RAND_egd() and ssl._test_decode_cert() support str with
   surrogates and bytes for the filename