diff --git a/test/excludes/Psych/TestDateTime.rb b/test/excludes/Psych/TestDateTime.rb
index 1188b4d4a6..63d99be809 100644
--- a/test/excludes/Psych/TestDateTime.rb
+++ b/test/excludes/Psych/TestDateTime.rb
@@ -1 +1,4 @@
-exclude(:test_new_datetime, "Psych loses the start date")
+exclude(:test_new_datetime, <<MSG)
+Undefined behavior of YAML spec, no definitions for pre Gregorian dates.
+https://github.com/yaml/yaml/issues/69
+MSG