diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 27a1616c6ebd9..eaf28db082459 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -219,6 +219,7 @@ set(TEST_MODES
     optimize_none_with_implicit_dynamic
     optimize_with_implicit_dynamic
     only_executable only_non_executable
+    with_cxx_interop
 )
 set(TEST_SUBSETS
     primary
diff --git a/test/lit.cfg b/test/lit.cfg
index 35e8625dd7215..a01380e092091 100644
--- a/test/lit.cfg
+++ b/test/lit.cfg
@@ -708,6 +708,10 @@ elif swift_test_mode == 'only_executable':
     config.limit_to_features.add("executable_test")
 elif swift_test_mode == 'only_non_executable':
     config.available_features.add("nonexecutable_test")
+elif swift_test_mode == 'with_cxx_interop':
+    config.available_features.add("with_cxx_interop")
+    config.swift_frontend_test_options += ' -enable-experimental-cxx-interop'
+    config.swift_driver_test_options += ' -Xfrontend -enable-experimental-cxx-interop'
 else:
     lit_config.fatal("Unknown test mode %r" % swift_test_mode)