diff --git a/contrib/test_decoding/expected/ddl.out b/contrib/test_decoding/expected/ddl.out
index 11b2d9c07f..57a1289ea7 100644
--- a/contrib/test_decoding/expected/ddl.out
+++ b/contrib/test_decoding/expected/ddl.out
@@ -12,7 +12,7 @@ ERROR:  replication slot "regression_slot" already exists
 -- fail because of an invalid name
 SELECT 'init' FROM pg_create_logical_replication_slot('Invalid Name', 'test_decoding');
 ERROR:  replication slot name "Invalid Name" contains invalid character
-HINT:  Replication slot names may only contain letters, numbers, and the underscore character.
+HINT:  Replication slot names may only contain lower case letters, numbers, and the underscore character.
 -- fail twice because of an invalid parameter values
 SELECT 'init' FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', 'frakbar');
 ERROR:  could not parse value "frakbar" for parameter "include-xids"
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index c66619cda2..a4b86e039e 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -196,7 +196,7 @@ ReplicationSlotValidateName(const char *name, int elevel)
 					(errcode(ERRCODE_INVALID_NAME),
 			errmsg("replication slot name \"%s\" contains invalid character",
 				   name),
-					 errhint("Replication slot names may only contain letters, numbers, and the underscore character.")));
+					 errhint("Replication slot names may only contain lower case letters, numbers, and the underscore character.")));
 			return false;
 		}
 	}