diff --git a/src/calibre/ptempfile.py b/src/calibre/ptempfile.py
index ad8da9dcb5..868f6dfdd7 100644
--- a/src/calibre/ptempfile.py
+++ b/src/calibre/ptempfile.py
@@ -7,19 +7,10 @@ being closed.
 import os
 import tempfile
 
-from calibre.constants import __appname__, __version__, filesystem_encoding, get_windows_temp_path, ismacos, iswindows
+from calibre.constants import __appname__, filesystem_encoding, get_windows_temp_path, ismacos, iswindows
 from calibre.utils.safe_atexit import remove_dir, remove_file_atexit, remove_folder_atexit, unlink
 
-_base_dir = None
-
-
-def app_prefix(prefix):
-    if iswindows:
-        return f'{__appname__}_'
-    return f'{__appname__}_{__version__}_{prefix}'
-
-
-_osx_cache_dir = None
+_base_dir = _osx_cache_dir = None
 
 
 def osx_cache_dir():
@@ -66,7 +57,7 @@ def base_dir():
             base = os.environ.get('CALIBRE_TEMP_DIR', None)
             if base is not None and iswindows:
                 base = os.getenv('CALIBRE_TEMP_DIR')
-            prefix = app_prefix('tmp_')
+            prefix = f'{__appname__}-'
             if base is None:
                 if iswindows:
                     # On windows, if the TMP env var points to a path that
diff --git a/src/calibre/test_build.py b/src/calibre/test_build.py
index 3e22902e73..8a23df108e 100644
--- a/src/calibre/test_build.py
+++ b/src/calibre/test_build.py
@@ -556,10 +556,6 @@ class BuildTest(unittest.TestCase):
 
 
 def test_multiprocessing():
-    if ismacos:
-        # skip because this tests fails on some macOS systems with
-        # OSError: AF_UNIX path too long. Sigh.
-        return
     from multiprocessing import get_all_start_methods, get_context
     for stype in get_all_start_methods():
         if stype == 'fork':