diff --git a/packages/babel-generator/src/generators/statements.js b/packages/babel-generator/src/generators/statements.js
index 12d516ae04..596983e009 100644
--- a/packages/babel-generator/src/generators/statements.js
+++ b/packages/babel-generator/src/generators/statements.js
@@ -1,7 +1,7 @@
 import repeating from "repeating";
 import * as t from "babel-types";
 
-const NON_ALPHABETIC_UNARY_OPERATORS = t.UPDATE_OPERATORS.concat(t.NUMBER_UNARY_OPERATORS).concat(['!']);
+const NON_ALPHABETIC_UNARY_OPERATORS = t.UPDATE_OPERATORS.concat(t.NUMBER_UNARY_OPERATORS).concat(["!"]);
 
 export function WithStatement(node: Object) {
   this.keyword("with");