diff --git a/docs/grammar.txt b/docs/grammar.txt
index 7bb45bba9..5fac96a1c 100644
--- a/docs/grammar.txt
+++ b/docs/grammar.txt
@@ -90,13 +90,16 @@ MemberAccess = Expression '.' Identifier
 IndexAccess = Expression '[' Expression? ']'
 
 BooleanLiteral = 'true' | 'false'
-NumberLiteral = '0x'? [0-9]+ (' ' NumberUnit)?
+NumberLiteral = ( HexNumber | DecimalNumber ) (' ' NumberUnit)?
 NumberUnit = 'wei' | 'szabo' | 'finney' | 'ether'
            | 'seconds' | 'minutes' | 'hours' | 'days' | 'weeks' | 'years'
 HexLiteral = 'hex' ('"' ([0-9a-fA-F]{2})* '"' | '\'' ([0-9a-fA-F]{2})* '\'')
 StringLiteral = '"' ([^"\r\n\\] | '\\' .)* '"'
 Identifier = [a-zA-Z_] [a-zA-Z_0-9]*
 
+HexNumber = '0x' [0-9a-fA-F]+
+DecimalNumber = [0-9]+
+
 ElementaryTypeName = 'address' | 'bool' | 'string' | 'var'
                    | Int | Uint | Byte | Fixed | Ufixed