[spec] Fix typo in rule

document/core/appendix/properties.rst

diff --git a/document/core/appendix/properties.rst b/document/core/appendix/properties.rst
index 39cb22b..c04d2be 100644
--- a/document/core/appendix/properties.rst
+++ b/document/core/appendix/properties.rst
@@ -270,7 +270,7 @@
      \qquad
      \vdashresulttype [t^\ast] : \OKresulttype
    }{
-     S \vdashresult (\REFEXNADDR~a)~\THROWREF : [{t'}^\ast]
+     S \vdashresult (\REFEXNADDR~a)~\THROWREF : [t^\ast]
    }