diff --git a/kaitai/expr.rkt b/kaitai/expr.rkt
index 67a05a3..eceb5be 100644
--- a/kaitai/expr.rkt
+++ b/kaitai/expr.rkt
@@ -6,8 +6,8 @@
          parser-tools/yacc)
 
 (define-tokens kaitai-expr [boolean number string identifier])
-(define-empty-tokens kaitai-sym [eof + - * / % < <= > >= == != << >> & pipe ^ not and or ? :
-                                   lparen rparen lbracket comma dot rbracket])
+(define-empty-tokens kaitai-sym [eof + - * / % < <= > >= == != << >> & pipe ^ not and or ? : ~
+                                 lparen rparen lbracket comma dot rbracket])
 
 (define (kaitai-numstr->number str)
   (match (regexp-replace* #px"_" str "")
@@ -52,6 +52,7 @@
     ["&" (token-&)]
     ["|" (token-pipe)]
     ["^" (token-^)]
+    ["~" (token-~)]
     ["not" (token-not)]
     ["and" (token-and)]
     ["or" (token-or)]
@@ -81,7 +82,7 @@
            (left & pipe ^)
            (left < <= > >= != ==)
            (left << >>)
-           (left + -)
+           (left + - ~)
            (left * / %)
            (right not)
            (left dot lparen rparen lbracket rbracket)]
@@ -112,6 +113,9 @@
            [(exp and exp) (list 'and $1 $3)]
            [(exp or exp) (list 'or $1 $3)]
            [(not exp) (list 'not $2)]
+           [(+ exp) (list '+ $2)]
+           [(- exp) (list '- $2)]
+           [(~ exp) (list '~ $2)]
            [(exp ? exp : exp) (list 'if $1 $3 $5)]
            [(lparen exp rparen) $2])
       (apply-args
@@ -119,7 +123,7 @@
         [(exp comma apply-args) (cons $1 $3)])
       ]))
 
-(define test2 "true and 'a' != 'b' ? 1 : ('hello' + 'world').substring(2, 3)")
+(define test2 "true and 'a' != 'b' ? -1 + ~bits : ('hello' + 'world').substring(2, 3)")
 
 (let ([input (open-input-string test2)])
   (kaitai-parser (lambda () (kaitai-lexer input))))