diff --git a/Lib/test/support.py b/Lib/test/support.py
--- a/Lib/test/support.py
+++ b/Lib/test/support.py
@@ -172,6 +172,9 @@
                 if not _save_and_block_module(blocked_name, orig_modules):
                     names_to_remove.append(blocked_name)
             fresh_module = importlib.import_module(name)
+            # Keep reference to fresh modules to prevent GC
+            fresh_module.__fresh = [importlib.import_module(fresh_name)
+                                    for fresh_name in fresh]
         except ImportError:
             fresh_module = None
         finally: