diff --git a/Lib/test/libregrtest/setup.py b/Lib/test/libregrtest/setup.py
index cb410da5acb4c3..793347f60ad93c 100644
--- a/Lib/test/libregrtest/setup.py
+++ b/Lib/test/libregrtest/setup.py
@@ -111,6 +111,8 @@ def setup_tests(runtests: RunTests):
     timeout = runtests.timeout
     if timeout is not None:
         # For a slow buildbot worker, increase SHORT_TIMEOUT and LONG_TIMEOUT
+        support.LOOPBACK_TIMEOUT = max(support.LOOPBACK_TIMEOUT, timeout / 120)
+        # don't increase INTERNET_TIMEOUT
         support.SHORT_TIMEOUT = max(support.SHORT_TIMEOUT, timeout / 40)
         support.LONG_TIMEOUT = max(support.LONG_TIMEOUT, timeout / 4)
 
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 900b9c96d08a64..f3270d66bd0852 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -75,13 +75,7 @@
 #
 # The timeout should be long enough for connect(), recv() and send() methods
 # of socket.socket.
-LOOPBACK_TIMEOUT = 5.0
-if sys.platform == 'win32' and ' 32 bit (ARM)' in sys.version:
-    # bpo-37553: test_socket.SendfileUsingSendTest is taking longer than 2
-    # seconds on Windows ARM32 buildbot
-    LOOPBACK_TIMEOUT = 10
-elif sys.platform == 'vxworks':
-    LOOPBACK_TIMEOUT = 10
+LOOPBACK_TIMEOUT = 10.0
 
 # Timeout in seconds for network requests going to the internet. The timeout is
 # short enough to prevent a test to wait for too long if the internet request