diff --git a/docs/_pages/grammar.md b/docs/_pages/grammar.md
index 22b078a1..c369eda9 100644
--- a/docs/_pages/grammar.md
+++ b/docs/_pages/grammar.md
@@ -60,6 +60,9 @@ unop = '-' | 'not' | '#'
 
 SimpleType =
     'nil' |
+    STRING |
+    'true' |
+    'false' |
     NAME ['.' NAME] [ '<' TypeList '>' ] |
     'typeof' '(' exp ')' |
     TableType |