diff --git a/sanitiser/_warn_quattroshapes.js b/sanitiser/_warn_quattroshapes.js
new file mode 100644
index 00000000..b4486cfe
--- /dev/null
+++ b/sanitiser/_warn_quattroshapes.js
@@ -0,0 +1,25 @@
+var _ = require('lodash');
+
+function setup( paramName, targetMap ) {
+  return function( raw, clean ){
+    return sanitize( raw, clean );
+  };
+}
+
+function sanitize( raw, clean, opts ) {
+  // error & warning messages
+  var messages = { errors: [], warnings: [] };
+
+  if (_.includes(raw.sources, 'quattroshapes') || _.includes(raw.sources, 'qs')) {
+    messages.warnings.push( 'You are using Quattroshapes as a data source in this query. ' +
+     'Quattroshapes will be disabled as a data source for Mapzen Search in the next several ' +
+     'weeks, and is being replaced by Who\'s on First, an actively maintained data project ' +
+     'based on Quattroshapes. Your existing queries WILL CONTINUE TO WORK for the foreseeable ' +
+     'future, but results will be coming from Who\'s on First and `source=quattroshapes` will ' +
+     'be deprecated. If you have any questions, please email search@mapzen.com.');
+  }
+
+  return messages;
+}
+
+module.exports = setup;
diff --git a/sanitiser/reverse.js b/sanitiser/reverse.js
index 154fd3d9..6ebcfd14 100644
--- a/sanitiser/reverse.js
+++ b/sanitiser/reverse.js
@@ -5,6 +5,7 @@ var sanitizeAll = require('../sanitiser/sanitizeAll'),
       singleScalarParameters: require('../sanitiser/_single_scalar_parameters'),
       layers: require('../sanitiser/_targets')('layers', type_mapping.layer_with_aliases_to_type),
       sources: require('../sanitiser/_targets')('sources', type_mapping.source_to_type),
+      quattroshapes_warning: require('../sanitiser/_warn_quattroshapes')(),
       size: require('../sanitiser/_size'),
       private: require('../sanitiser/_flag_bool')('private', false),
       geo_reverse: require('../sanitiser/_geo_reverse'),
diff --git a/sanitiser/search.js b/sanitiser/search.js
index cc596b26..75be20ca 100644
--- a/sanitiser/search.js
+++ b/sanitiser/search.js
@@ -7,6 +7,7 @@ var sanitizeAll = require('../sanitiser/sanitizeAll'),
       size: require('../sanitiser/_size'),
       layers: require('../sanitiser/_targets')('layers', type_mapping.layer_with_aliases_to_type),
       sources: require('../sanitiser/_targets')('sources', type_mapping.source_to_type),
+      quattroshapes_warning: require('../sanitiser/_warn_quattroshapes')(),
       private: require('../sanitiser/_flag_bool')('private', false),
       geo_search: require('../sanitiser/_geo_search'),
       boundary_country: require('../sanitiser/_boundary_country'),
diff --git a/test/unit/sanitiser/reverse.js b/test/unit/sanitiser/reverse.js
index 4e727b5b..d9fdebc9 100644
--- a/test/unit/sanitiser/reverse.js
+++ b/test/unit/sanitiser/reverse.js
@@ -38,7 +38,8 @@ module.exports.tests.interface = function(test, common) {
 
 module.exports.tests.sanitisers = function(test, common) {
   test('check sanitiser list', function (t) {
-    var expected = ['singleScalarParameters', 'layers', 'sources', 'size', 'private', 'geo_reverse', 'boundary_country'];
+    var expected = [ 'singleScalarParameters', 'layers', 'sources', 'quattroshapes_warning',
+      'size', 'private', 'geo_reverse', 'boundary_country' ];
     t.deepEqual(Object.keys(reverse.sanitiser_list), expected);
     t.end();
   });
diff --git a/test/unit/sanitiser/search.js b/test/unit/sanitiser/search.js
index b00160dd..07178626 100644
--- a/test/unit/sanitiser/search.js
+++ b/test/unit/sanitiser/search.js
@@ -24,7 +24,8 @@ module.exports.tests.interface = function(test, common) {
 
 module.exports.tests.sanitisers = function(test, common) {
   test('check sanitiser list', function (t) {
-    var expected = ['singleScalarParameters', 'text', 'size', 'layers', 'sources', 'private', 'geo_search', 'boundary_country' ];
+    var expected = [ 'singleScalarParameters', 'text', 'size', 'layers', 'sources',
+      'quattroshapes_warning', 'private', 'geo_search', 'boundary_country' ];
     t.deepEqual(Object.keys(search.sanitiser_list), expected);
     t.end();
   });