diff --git a/sanitiser/_geo_search.js b/sanitiser/_geo_search.js
index 0e5ec896..8aef9b7f 100644
--- a/sanitiser/_geo_search.js
+++ b/sanitiser/_geo_search.js
@@ -1,3 +1,4 @@
+var check = require('check-types');
 var geo_common = require ('./_geo_common');
 var LAT_LON_IS_REQUIRED = false;
 var RECT_IS_REQUIRED = false;
@@ -10,6 +11,17 @@ module.exports = function sanitize( raw, clean ){
   // error & warning messages
   var messages = { errors: [], warnings: [] };
 
+  // disallow specifying both focus.point and focus.viewport
+  if ( ( raw['focus.viewport.min_lat'] ||
+         raw['focus.viewport.max_lat'] ||
+         raw['focus.viewport.min_lon'] ||
+         raw['focus.viewport.max_lon'] )  &&
+       ( raw['focus.point.lat'] ||
+         raw['focus.point.lon'] ) ) {
+    messages.errors.push( 'focus.point and focus.viewport can\'t both be set' );
+    return messages;
+  }
+
   try {
     geo_common.sanitize_point( 'focus.point', clean, raw, LAT_LON_IS_REQUIRED );
     geo_common.sanitize_rect( 'boundary.rect', clean, raw, RECT_IS_REQUIRED );
diff --git a/test/unit/sanitiser/search.js b/test/unit/sanitiser/search.js
index eed05ee6..4f4e2880 100644
--- a/test/unit/sanitiser/search.js
+++ b/test/unit/sanitiser/search.js
@@ -227,6 +227,53 @@ module.exports.tests.sanitize_viewport = function(test, common) {
       t.end();
     });
   });
+
+  test('error returned if focus.point and focus.viewpoint specified', function(t) {
+    var req = {
+      query: {
+        text: 'test',
+        'focus.point.lat': '10',
+        'focus.point.lon': '15',
+        '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], 'focus.point and focus.viewport can\'t both be set', 'no error');
+      t.notOk(req.clean.hasOwnProperty('focus.viewport.min_lat'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.viewport.max_lat'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.viewport.min_lon'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.viewport.max_lon'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.point.lat'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.point.lon'), 'clean should be empty');
+      t.end();
+    });
+  });
+
+  test('error returned if focus.point and focus.viewpoint partially specified', function(t) {
+    var req = {
+      query: {
+        text: 'test',
+        'focus.point.lat': '10',
+        'focus.viewport.min_lat': '37',
+        'focus.viewport.max_lon': '-122'
+      }
+    };
+
+    sanitize(req, function() {
+      t.equal(req.errors[0], 'focus.point and focus.viewport can\'t both be set', 'no error');
+      t.notOk(req.clean.hasOwnProperty('focus.viewport.min_lat'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.viewport.max_lat'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.viewport.min_lon'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.viewport.max_lon'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.point.lat'), 'clean should be empty');
+      t.notOk(req.clean.hasOwnProperty('focus.point.lon'), 'clean should be empty');
+      t.end();
+    });
+  });
 };
 
 module.exports.tests.sanitize_size = function(test, common) {