diff --git a/Lib/base64.py b/Lib/base64.py
index 2be9c395a96674..6996244d8e2eae 100755
--- a/Lib/base64.py
+++ b/Lib/base64.py
@@ -28,9 +28,17 @@
     'urlsafe_b64encode', 'urlsafe_b64decode',
     ]
 
-
+VALID_BASE64_REGEX = None
 bytes_types = (bytes, bytearray)  # Types acceptable as binary data
 
+def _get_valid_base64_regex():
+    global VALID_BASE64_REGEX
+    if VALID_BASE64_REGEX:
+        return VALID_BASE64_REGEX
+
+    VALID_BASE64_REGEX = re.compile(b'^[A-Za-z0-9+/]*={0,2}$')
+    return VALID_BASE64_REGEX
+
 def _bytes_from_decode_data(s):
     if isinstance(s, str):
         try:
@@ -82,7 +90,7 @@ def b64decode(s, altchars=None, validate=False):
         altchars = _bytes_from_decode_data(altchars)
         assert len(altchars) == 2, repr(altchars)
         s = s.translate(bytes.maketrans(altchars, b'+/'))
-    if validate and not re.match(b'^[A-Za-z0-9+/]*={0,2}$', s):
+    if validate and not _get_valid_base64_regex().match(s):
         raise binascii.Error('Non-base64 digit found')
     return binascii.a2b_base64(s)