diff --git a/bin/cbuildbot.py b/bin/cbuildbot.py
index 721dd70573..d58a72727b 100755
--- a/bin/cbuildbot.py
+++ b/bin/cbuildbot.py
@@ -406,8 +406,8 @@ def _ArchiveTestResults(buildroot, board, archive_dir, test_results_dir):
     dir_entries = os.listdir(ARCHIVE_BASE)
     if len(dir_entries) >= ARCHIVE_COUNT:
       oldest_dirs = heapq.nsmallest((len(dir_entries) - ARCHIVE_COUNT) + 1,
-                                    [filename for filename in dir_entries],
-                                    key=lambda fn: os.stat(fn).st_mtime)
+          [os.path.join(ARCHIVE_BASE, filename) for filename in dir_entries],
+          key=lambda fn: os.stat(fn).st_mtime)
       Info('Removing archive dirs %s' % oldest_dirs)
       for oldest_dir in oldest_dirs:
         shutil.rmtree(os.path.join(ARCHIVE_BASE, oldest_dir))
diff --git a/bin/cbuildbot_unittest.py b/bin/cbuildbot_unittest.py
index e699f0c9cb..bbbc56c6f7 100755
--- a/bin/cbuildbot_unittest.py
+++ b/bin/cbuildbot_unittest.py
@@ -131,8 +131,8 @@ class CBuildBotTest(mox.MoxTestBase):
     # Expected calls.
     os.path.exists(cbuildbot.ARCHIVE_BASE).AndReturn(True)
     os.listdir(os.path.join(cbuildbot.ARCHIVE_BASE)).AndReturn(dir_listing)
-    os.stat('file1').AndReturn(stat1)
-    os.stat('file2').AndReturn(stat2)
+    os.stat(os.path.join(cbuildbot.ARCHIVE_BASE, 'file1')).AndReturn(stat1)
+    os.stat(os.path.join(cbuildbot.ARCHIVE_BASE, 'file2')).AndReturn(stat2)
     # Should remove the oldest path.
     shutil.rmtree(os.path.join(cbuildbot.ARCHIVE_BASE, 'file2'))
 
@@ -145,7 +145,7 @@ class CBuildBotTest(mox.MoxTestBase):
     os.path.exists(path_to_archive_dir).AndReturn(False)
     cbuildbot.RunCommand(['sudo', 'chmod', '-R', '+r', path_to_results])
     shutil.copytree(path_to_results, path_to_archive_dir)
-    cbuildbot.RunCommand(['gzip', '-f', path_to_image])
+    cbuildbot.RunCommand(['gzip', '-f', '--fast', path_to_image])
     shutil.copyfile(path_to_image + '.gz', os.path.join(
         path_to_archive_dir, 'chromiumos_qemu_image.bin.gz'))