diff --git a/core/modules/simpletest/tests/system_incompatible_core_version_test.info b/core/modules/simpletest/tests/system_incompatible_core_version_test.info
index 7b138ee..13d6525 100644
--- a/core/modules/simpletest/tests/system_incompatible_core_version_test.info
+++ b/core/modules/simpletest/tests/system_incompatible_core_version_test.info
@@ -2,5 +2,6 @@ name = "System incompatible core version test"
 description = "Support module for testing system dependencies."
 package = Testing
 version = VERSION
+; @todo This version string should be updated in the 8.x to 9.x migration.
 core = 9.x
 hidden = TRUE