diff --git a/Doc/ref/ref7.tex b/Doc/ref/ref7.tex
index 7459412..a285c4c 100644
--- a/Doc/ref/ref7.tex
+++ b/Doc/ref/ref7.tex
@@ -439,7 +439,7 @@
              {"class" \token{classname} [\token{inheritance}] ":"
               \token{suite}}
   \production{inheritance}
-             {"(" \token{expression_list} ")"}
+             {"(" [\token{expression_list}] ")"}
   \production{classname}
              {\token{identifier}}
 \end{productionlist}