diff --git a/libs/fcache/cache.py b/libs/fcache/cache.py
index f6f1d9cb2..32a8a769b 100644
--- a/libs/fcache/cache.py
+++ b/libs/fcache/cache.py
@@ -40,7 +40,7 @@ class FileCache(MutableMapping):
 
     :param str appname: The app/script the cache should be associated with.
     :param str flag: How the cache should be opened. See below for details.
-    :param mode: The Unix mode for the cache files.
+    :param mode: The Unix mode for the cache files or False to prevent changing permissions.
     :param str keyencoding: The encoding the keys use, defaults to 'utf-8'.
         This is used if *serialize* is ``False``; the keys are treated as
         :class:`bytes` objects.
@@ -247,7 +247,8 @@ class FileCache(MutableMapping):
         with os.fdopen(fh, self._flag) as f:
             f.write(self._dumps(bytesvalue))
         rename(tmp, filename)
-        os.chmod(filename, self._mode)
+        if self._mode:
+            os.chmod(filename, self._mode)
 
     def _read_from_file(self, filename):
         """Read data from filename."""
@@ -256,7 +257,7 @@ class FileCache(MutableMapping):
                 return self._loads(f.read())
         except (IOError, OSError):
             logger.warning('Error opening file: {}'.format(filename))
-            raise
+            return None
 
     def __setitem__(self, key, value):
         ekey = self._encode_key(key)
diff --git a/libs/fcache/posixemulation.py b/libs/fcache/posixemulation.py
index cf9ac63b7..03d6982c3 100644
--- a/libs/fcache/posixemulation.py
+++ b/libs/fcache/posixemulation.py
@@ -46,7 +46,15 @@ if os.name == 'nt':  # pragma: no cover
                 dst = unicode(dst, sys.getfilesystemencoding())
             if _rename_atomic(src, dst):
                 return True
-            return _MoveFileEx(src, dst, _MOVEFILE_REPLACE_EXISTING | _MOVEFILE_WRITE_THROUGH)
+            retry = 0
+            rv = False
+            while not rv and retry < 100:
+                rv = _MoveFileEx(src, dst, _MOVEFILE_REPLACE_EXISTING |
+                                 _MOVEFILE_WRITE_THROUGH)
+                if not rv:
+                    time.sleep(0.001)
+                    retry += 1
+            return rv
 
         # new in Vista and Windows Server 2008
         _CreateTransaction = ctypes.windll.ktmw32.CreateTransaction
@@ -60,11 +68,18 @@ if os.name == 'nt':  # pragma: no cover
             if ta == -1:
                 return False
             try:
-                rv = _MoveFileTransacted(src, dst, None, None,
-                                         _MOVEFILE_REPLACE_EXISTING |
-                                         _MOVEFILE_WRITE_THROUGH, ta)
-                if rv:
-                    rv = _CommitTransaction(ta)
+                retry = 0
+                rv = False
+                while not rv and retry < 100:
+                    rv = _MoveFileTransacted(src, dst, None, None,
+                                             _MOVEFILE_REPLACE_EXISTING |
+                                             _MOVEFILE_WRITE_THROUGH, ta)
+                    if rv:
+                        rv = _CommitTransaction(ta)
+                        break
+                    else:
+                        time.sleep(0.001)
+                        retry += 1
                 return rv
             finally:
                 _CloseHandle(ta)
@@ -77,7 +92,7 @@ if os.name == 'nt':  # pragma: no cover
             return
         # Fall back to "move away and replace"
         try:
-            shutil.move(src, dst)
+            os.rename(src, dst)
         except OSError as e:
             if e.errno != errno.EEXIST:
                 raise
diff --git a/libs/subzero/cache_backends/file.py b/libs/subzero/cache_backends/file.py
index d72d7b84a..a97c8fad2 100644
--- a/libs/subzero/cache_backends/file.py
+++ b/libs/subzero/cache_backends/file.py
@@ -8,7 +8,8 @@ class SZFileBackend(CacheBackend):
     def __init__(self, arguments):
         self._cache = FileCache(arguments.pop("appname", None), flag=arguments.pop("flag", "c"),
                                 serialize=arguments.pop("serialize", True),
-                                app_cache_dir=arguments.pop("app_cache_dir", None))
+                                app_cache_dir=arguments.pop("app_cache_dir", None),
+                                mode=False)
 
     def get(self, key):
         value = self._cache.get(key, NO_VALUE)
diff --git a/libs/version.txt b/libs/version.txt
index 8316736be..13afd5a8e 100644
--- a/libs/version.txt
+++ b/libs/version.txt
@@ -128,7 +128,7 @@ webencodings==0.5.1
 
 # Required-by: subzero
 backports.functools-lru-cache==1.6.4
-fcache==0.4.7
+fcache==0.4.7 # https://github.com/tsroten/fcache/pull/34
 json_tricks==3.16.1
 tld==0.12.6 # https://github.com/barseghyanartur/tld/pull/119