diff --git a/libcxx/utils/libcxx/test/params.py b/libcxx/utils/libcxx/test/params.py
--- a/libcxx/utils/libcxx/test/params.py
+++ b/libcxx/utils/libcxx/test/params.py
@@ -111,7 +111,7 @@
             ]),
 
   # Parameters to enable or disable parts of the test suite
-  Parameter(name='enable_experimental', choices=[True, False], type=bool, default=False,
+  Parameter(name='enable_experimental', choices=[True, False], type=bool, default=True,
             help="Whether to enable tests for experimental C++ libraries (typically Library Fundamentals TSes).",
             actions=lambda experimental: [] if not experimental else [
               AddFeature('c++experimental'),