diff --git a/src/impl/regexParser.js b/src/impl/regexParser.js
index 0b0297b1f..628108a82 100644
--- a/src/impl/regexParser.js
+++ b/src/impl/regexParser.js
@@ -229,7 +229,7 @@ function extractRFC2822(match) {
 function preprocessRFC2822(s) {
   // Remove comments and folding whitespace and replace multiple-spaces with a single space
   return s
-    .replace(/\([^)]*\)|[\n\t]/g, " ")
+    .replace(/\([^()]*\)|[\n\t]/g, " ")
     .replace(/(\s\s+)/g, " ")
     .trim();
 }