diff --git a/sanitiser/_geo_search.js b/sanitiser/_geo_search.js
index badeec52..0e5ec896 100644
--- a/sanitiser/_geo_search.js
+++ b/sanitiser/_geo_search.js
@@ -2,6 +2,7 @@ var geo_common = require ('./_geo_common');
 var LAT_LON_IS_REQUIRED = false;
 var RECT_IS_REQUIRED = false;
 var CIRCLE_IS_REQUIRED = false;
+var VIEWPORT_IS_REQUIRED = false;
 
 // validate inputs, convert types and apply defaults
 module.exports = function sanitize( raw, clean ){
@@ -13,6 +14,7 @@ module.exports = function sanitize( raw, clean ){
     geo_common.sanitize_point( 'focus.point', clean, raw, LAT_LON_IS_REQUIRED );
     geo_common.sanitize_rect( 'boundary.rect', clean, raw, RECT_IS_REQUIRED );
     geo_common.sanitize_circle( 'boundary.circle', clean, raw, CIRCLE_IS_REQUIRED );
+    geo_common.sanitize_rect( 'focus.viewport', clean, raw, VIEWPORT_IS_REQUIRED );
   }
   catch (err) {
     messages.errors.push( err.message );
diff --git a/test/unit/sanitiser/search.js b/test/unit/sanitiser/search.js
index 2b171406..eed05ee6 100644
--- a/test/unit/sanitiser/search.js
+++ b/test/unit/sanitiser/search.js
@@ -207,6 +207,28 @@ module.exports.tests.sanitize_bounding_rect = function(test, common) {
   });
 };
 
+module.exports.tests.sanitize_viewport = function(test, common) {
+  test('valid viewport', function(t) {
+    var req = {
+      query: {
+        text: 'test',
+        'focus.viewport.min_lat': '37',
+        'focus.viewport.max_lat': '38',
+        'focus.viewport.min_lon': '-123',
+        'focus.viewport.max_lon': '-122'
+      }
+    };
+    sanitize(req, function() {
+      t.equal(req.errors[0], undefined, 'no error');
+      t.equal(req.clean['focus.viewport.min_lat'], parseFloat(req.query['focus.viewport.min_lat']), 'correct min_lat in clean');
+      t.equal(req.clean['focus.viewport.max_lat'], parseFloat(req.query['focus.viewport.max_lat']), 'correct max_lat in clean');
+      t.equal(req.clean['focus.viewport.min_lon'], parseFloat(req.query['focus.viewport.min_lon']), 'correct min_lon in clean');
+      t.equal(req.clean['focus.viewport.max_lon'], parseFloat(req.query['focus.viewport.max_lon']), 'correct max_lon in clean');
+      t.end();
+    });
+  });
+};
+
 module.exports.tests.sanitize_size = function(test, common) {
   test('invalid size value', function(t) {
     var req = { query: { size: 'a', text: 'test', lat: 0, lon: 0 } };