diff --git a/doc/ref/spec.md b/doc/ref/spec.md
index e46add0..7fd5f5e 100644
--- a/doc/ref/spec.md
+++ b/doc/ref/spec.md
@@ -285,7 +285,7 @@
 
 ```
 int_lit     = decimal_lit | si_lit | octal_lit | binary_lit | hex_lit .
-decimal_lit = ( "1" … "9" ) { [ "_" ] decimal_digit } .
+decimal_lit = "0" | ( "1" … "9" ) { [ "_" ] decimal_digit } .
 decimals    = decimal_digit { [ "_" ] decimal_digit } .
 si_it       = decimals [ "." decimals ] multiplier |
               "." decimals  multiplier .