diff --git a/src/sqlParser.jison b/src/sqlParser.jison
@@ -50,6 +50,7 @@ IN                                                                return 'IN'
SOUNDS                                                            return 'SOUNDS'
LIKE                                                              return 'LIKE'
ESCAPE                                                            return 'ESCAPE'
REGEXP                                                            return 'REGEXP'
IS                                                                return 'IS'
UNKNOWN                                                           return 'UNKNOWN'
@@ -343,6 +344,9 @@ case_when_else
case_when
  : CASE case_expr_opt when_then_list case_when_else END { $$ = { type: 'CaseWhen', caseExprOpt: $2, whenThenList: $3, else: $4 } }
  ;
simple_expr_prefix
  : '+' simple_expr %prec UPLUS { $$ = { type: 'Prefix', prefix: $1, value: $2 } }
  | '-' simple_expr %prec UMINUS { $$ = { type: 'Prefix', prefix: $1, value: $2 } }
@@ -361,6 +365,7 @@ simple_expr
  | EXISTS '(' selectClause ')' { $$ = { type: 'SubQuery', value: $3, hasExists: true } }
  | '{' identifier expr '}' { $$ = { type: 'IdentifierExpr', identifier: $2, value: $3 } }
  | case_when { $$ = $1 }
  ;
bit_expr
  : simple_expr { $$ = $1 }

diff --git a/src/stringify.js b/src/stringify.js
@@ -225,6 +225,14 @@ Sql.prototype.travelCaseWhen = function(ast) {
  }
  this.appendKeyword('end');
};
Sql.prototype.travelPrefix = function(ast) {
  this.appendKeyword(ast.prefix);
  this.travel(ast.value);