diff --git a/spec/19-grammar.md b/spec/19-grammar.md
index ae4117b..4812dfc 100644
--- a/spec/19-grammar.md
+++ b/spec/19-grammar.md
@@ -277,7 +277,7 @@ The grammar notation is described in [Grammars section](09-lexical-structure.md#
    [   ]   (   )   {   }   .   ->   ++   --   **   *   +   -   ~   !
    $   /   %   <<   >>   <   >   <=   >=   ==   ===   !=   !==   ^   |
    &   &&   ||   ?   :   ;   =   **=   *=   /=   %=   +=   -=   .=   <<=
-   >>=   &=   ^=   |=   ,   ??   <=>   ...   \
+   >>=   &=   ^=   |=   ??=   ,   ??   <=>   ...   \
 </pre>
 
 ## Syntactic Grammar