diff --git a/README.md b/README.md
index 52e74f77..7856a345 100644
--- a/README.md
+++ b/README.md
@@ -139,7 +139,7 @@ Mailbox object is with the following structure
   * **root** (boolean) `true` if the node is root
   * **name** (string) unicode decoded name of the mailbox
   * **path** (string) full path to the mailbox
-  * **delimiter** (string) path delimiting symbol
+  * **delimiter** (string) path delimiting symbol.  In the event the server returns NIL for this (some servers do this for the INBOX), it will be coerced to a '/' at this time, but the behavior may be changed in the future depending on how the folder creation API is implemented.
   * **listed** (boolean) mailbox was found in the LIST response
   * **subscribed** (boolean) mailbox was found in the LSUB response
   * **specialUse** (string) mailbox was identified as a special use mailbox ('\Trash', '\Sent', '\Junk' etc. see [RFC6154](http://tools.ietf.org/html/rfc6154#section-2))
@@ -247,7 +247,7 @@ Namespace object is with the following structure
 Namespace element object has the following structure
 
   * **prefix** is the prefix string
-  * **delimiter** is the hierarchy delimiter
+  * **delimiter** is the hierarchy delimiter.  This can be null for some servers but will usually be a string.
 
 **NB!** Namespace_Response_Extensions are not supported (extension data is silently skipped)
 
diff --git a/src/browserbox.js b/src/browserbox.js
index e90a7237..38ea1f6a 100644
--- a/src/browserbox.js
+++ b/src/browserbox.js
@@ -1196,7 +1196,8 @@
                 return !arr ? false : [].concat(arr || []).map(function(ns) {
                     return !ns || !ns.length ? false : {
                         prefix: ns[0].value,
-                        delimiter: ns[1].value
+                        // The delimiter can legally be NIL which maps to null
+                        delimiter: ns[1] && ns[1].value
                     };
                 });
             };
diff --git a/test/unit/browserbox-test.js b/test/unit/browserbox-test.js
index 3c1b7c1c..14664cdb 100644
--- a/test/unit/browserbox-test.js
+++ b/test/unit/browserbox-test.js
@@ -1194,7 +1194,25 @@
                         delimiter: '/'
                     }]
                 });
+            });
 
+            it('should handle NIL namespace hierarchy delim', function() {
+                expect(br._parseNAMESPACE({
+                    payload: {
+                        NAMESPACE: [
+                            // This specific value is returned by yahoo.co.jp's
+                            // imapgate version 0.7.68_11_1.61475 IMAP server
+                            imapHandler.parser('* NAMESPACE (("" NIL)) NIL NIL')
+                        ]
+                    }
+                })).to.deep.equal({
+                    personal: [{
+                        prefix: '',
+                        delimiter: null
+                    }],
+                    users: false,
+                    shared: false
+                });
             });
         });