diff --git a/docs/lang.rst b/docs/lang.rst
index 9c4152ff..3c3f463b 100644
--- a/docs/lang.rst
+++ b/docs/lang.rst
@@ -63,7 +63,7 @@ section                                          status     comments
 5.6.1 Library Syntax                             incomplete In picrin, libraries can be reopend and can be nested.
 5.6.2 Library example                            N/A
 5.7 The REPL                                     yes
-6.1 Equivalence predicates                       yes        TODO: equal? must terminate if circular structure is given
+6.1 Equivalence predicates                       yes
 6.2.1 Numerical types                            yes        picrin has only two types of internal representation of numbers: fixnum and double float. It still comforms the R7RS spec.
 6.2.2 Exactness                                  yes
 6.2.3 Implementation restrictions                yes