diff --git a/sanitiser/_boundary_country.js b/sanitiser/_boundary_country.js
index f2824cec..192a9167 100644
--- a/sanitiser/_boundary_country.js
+++ b/sanitiser/_boundary_country.js
@@ -1,4 +1,4 @@
-var isObject = require('is-object');
+var check = require('check-types');
 var iso3166 = require('iso3166-1');
 
 function sanitize(raw, clean) {
@@ -8,23 +8,25 @@ function sanitize(raw, clean) {
   // init clean.boundary (if not already init)
   clean.boundary = clean.boundary || {};
 
-  if (raw['boundary.country']) {
+  if (check.assigned(raw['boundary.country'])) {
     var country = raw['boundary.country'];
 
-    if (typeof country !== 'string') {
+    if (!check.string(country)) {
       messages.warnings.push('boundary.country is not a string');
-      clean.boundary.country = undefined;
+      delete clean.boundary.country;
     }
     else if (!containsIsoCode(country.toUpperCase())) {
       messages.warnings.push(country + ' is not a valid ISO2/ISO3 country code');
-      clean.boundary.country = undefined;
+      delete clean.boundary.country;
     }
     else {
+      // the only way for boundary.country to be assigned is if input is
+      //  a string and a known ISO2 or ISO3
       clean.boundary.country = iso3166.to3(country.toUpperCase());
     }
 
   } else {
-    clean.boundary.country = undefined;
+    delete clean.boundary.country;
   }
 
   return messages;
diff --git a/test/unit/sanitiser/reverse.js b/test/unit/sanitiser/reverse.js
index 1529c1e1..f181b69b 100644
--- a/test/unit/sanitiser/reverse.js
+++ b/test/unit/sanitiser/reverse.js
@@ -10,7 +10,7 @@ var reverse  = require('../../../sanitiser/reverse'),
                       size: 10,
                       details: true,
                       categories: [],
-                      boundary: { country: undefined }
+                      boundary: { }
                     },
     sanitize = function(query, cb) { _sanitize({'query':query}, cb); };