diff --git a/README.md b/README.md
index d17e968..68e6bdb 100644
--- a/README.md
+++ b/README.md
@@ -564,13 +564,13 @@ Valid `options` are:
 
   * **headers** - < _mixed_ > - An _array_ of specific headers to retrieve, _boolean_ true to fetch all headers, or an _object_ of the form (**Default:** (no headers)):
 
-      * **fields** - < _mixed_ > - An _array_ of specific headers to retrieve or _boolean_ true to fetch all headers.
+      * **fields** - < _mixed_ > - An _array_ of specific headers to retrieve or _boolean_ true to fetch all headers. **Default:** (all headers)
 
       * **parse** - < _boolean_ > - Parse headers? **Default:** true
 
   * **headersNot** - < _mixed_ > - An _array_ of specific headers to exclude or an _object_ of the form (**Default:** (no headers)):
 
-      * **fields** - < _mixed_ > - An _array_ of specific headers to exclude.
+      * **fields** - < _mixed_ > - An _array_ of specific headers to exclude. **Default:** (all headers)
 
       * **parse** - < _boolean_ > - Parse headers? **Default:** true
 
diff --git a/lib/imap.js b/lib/imap.js
index fa846c1..dd18f21 100644
--- a/lib/imap.js
+++ b/lib/imap.js
@@ -996,6 +996,8 @@ ImapConnection.prototype._fetch = function(which, uids, options, what, cb) {
           if (Array.isArray(wp.headers))
             headers = wp.headers;
           else if (typeof wp.headers === 'object') {
+            if (wp.headers.fields === undefined)
+              wp.headers.fields = true;
             if (!Array.isArray(wp.headers.fields)
                 && typeof wp.headers.fields !== 'string'
                 && wp.headers.fields !== true)
@@ -1026,6 +1028,8 @@ ImapConnection.prototype._fetch = function(which, uids, options, what, cb) {
           if (Array.isArray(wp.headersNot))
             headers = wp.headersNot;
           else if (typeof wp.headersNot === 'object') {
+            if (wp.headersNot.fields === undefined)
+              wp.headersNot.fields = true;
             if (!Array.isArray(wp.headersNot.fields)
                 && typeof wp.headersNot.fields !== 'string'
                 && wp.headersNot.fields !== true)