--- a/toolkit/components/search/nsSearchService.js
+++ b/toolkit/components/search/nsSearchService.js
@@ -1773,25 +1773,36 @@ Engine.prototype = {
   _parseURL: function SRCH_ENG_parseURL(aElement) {
     var type     = aElement.getAttribute("type");
     // According to the spec, method is optional, defaulting to "GET" if not
     // specified
     var method   = aElement.getAttribute("method") || "GET";
     var template = aElement.getAttribute("template");
     var resultDomain = aElement.getAttribute("resultdomain");
 
+    let rels = [];
+    if (aElement.hasAttribute("rel")) {
+      rels = aElement.getAttribute("rel").toLowerCase().split(/\s+/);
+    }
+
+    // Support an alternate suggestion type, see bug 1425827 for details.
+    if (type == "application/json" && rels.includes("suggestions")) {
+      type = URLTYPE_SUGGEST_JSON;
+    }
+
     try {
       var url = new EngineURL(type, method, template, resultDomain);
     } catch (ex) {
       FAIL("_parseURL: failed to add " + template + " as a URL",
            Cr.NS_ERROR_FAILURE);
     }
 
-    if (aElement.hasAttribute("rel"))
-      url.rels = aElement.getAttribute("rel").toLowerCase().split(/\s+/);
+    if (rels.length) {
+      url.rels = rels;
+    }
 
     for (var i = 0; i < aElement.children.length; ++i) {
       var param = aElement.children[i];
       if (param.localName == "Param") {
         try {
           url.addParam(param.getAttribute("name"), param.getAttribute("value"));
         } catch (ex) {
           // Ignore failure

--- a/toolkit/components/search/tests/xpcshell/data/engineMaker.sjs
+++ b/toolkit/components/search/tests/xpcshell/data/engineMaker.sjs
@@ -28,25 +28,29 @@ function handleRequest(request, response
  */
 function createOpenSearchEngine(response, engineData) {
   let params = "", queryString = "";
   if (engineData.method == "POST") {
     params = "<Param name='q' value='{searchTerms}'/>";
   } else {
     queryString = "?q={searchTerms}";
   }
+  let type = "type='application/x-suggestions+json'";
+  if (engineData.alternativeJSONType) {
+    type = "type='application/json' rel='suggestions'";
+  }
 
-  let result = "<?xml version='1.0' encoding='utf-8'?>\
-<OpenSearchDescription xmlns='http://a9.com/-/spec/opensearch/1.1/'>\
-  <ShortName>" + engineData.name + "</ShortName>\
-  <Description>" + engineData.description + "</Description>\
-  <InputEncoding>UTF-8</InputEncoding>\
-  <LongName>" + engineData.name + "</LongName>\
-  <Url type='application/x-suggestions+json' method='" + engineData.method + "'\
-       template='" + engineData.baseURL + "searchSuggestions.sjs" + queryString + "'>\
-    " + params + "\
-  </Url>\
-  <Url type='text/html' method='" + engineData.method + "'\
-       template='" + engineData.baseURL + queryString + "'/>\
-</OpenSearchDescription>\
-";
+  let result = `<?xml version='1.0' encoding='utf-8'?>
+<OpenSearchDescription xmlns='http://a9.com/-/spec/opensearch/1.1/'>
+  <ShortName>${engineData.name}</ShortName>
+  <Description>${engineData.description}</Description>
+  <InputEncoding>UTF-8</InputEncoding>
+  <LongName>${engineData.name}</LongName>
+  <Url ${type} method='${engineData.method}'
+       template='${engineData.baseURL}searchSuggestions.sjs${queryString}'>
+    ${params}
+  </Url>
+  <Url type='text/html' method='${engineData.method}'
+       template='${engineData.baseURL}${queryString}'/>
+</OpenSearchDescription>
+`;
   response.write(result);
 }

--- a/toolkit/components/search/tests/xpcshell/test_searchSuggest.js
+++ b/toolkit/components/search/tests/xpcshell/test_searchSuggest.js
@@ -16,17 +16,17 @@ ChromeUtils.import("resource://gre/modul
 // We must make sure the FormHistoryStartup component is
 // initialized in order for it to respond to FormHistory
 // requests from nsFormAutoComplete.js.
 var formHistoryStartup = Cc["@mozilla.org/satchel/form-history-startup;1"].
                          getService(Ci.nsIObserver);
 formHistoryStartup.observe(null, "profile-after-change", null);
 
 var httpServer = new HttpServer();
-var getEngine, postEngine, unresolvableEngine;
+var getEngine, postEngine, unresolvableEngine, alternateJSONEngine;
 
 function run_test() {
   Services.prefs.setBoolPref("browser.search.suggest.enabled", true);
 
   let server = useHttpServer();
   server.registerContentType("sjs", "sjs");
 
   registerCleanupFunction(() => (async function cleanup() {
@@ -52,29 +52,40 @@ add_task(async function add_test_engines
   };
 
   let unresolvableEngineData = {
     baseURL: "http://example.invalid/",
     name: "Offline suggestion engine",
     method: "GET",
   };
 
-  [getEngine, postEngine, unresolvableEngine] = await addTestEngines([
+  let alternateJSONSuggestEngineData = {
+    baseURL: gDataUrl,
+    name: "Alternative JSON suggestion type",
+    method: "GET",
+    alternativeJSONType: true,
+  };
+
+  [getEngine, postEngine, unresolvableEngine, alternateJSONEngine] = await addTestEngines([
     {
       name: getEngineData.name,
       xmlFileName: "engineMaker.sjs?" + JSON.stringify(getEngineData),
     },
     {
       name: postEngineData.name,
       xmlFileName: "engineMaker.sjs?" + JSON.stringify(postEngineData),
     },
     {
       name: unresolvableEngineData.name,
       xmlFileName: "engineMaker.sjs?" + JSON.stringify(unresolvableEngineData),
     },
+    {
+      name: alternateJSONSuggestEngineData.name,
+      xmlFileName: "engineMaker.sjs?" + JSON.stringify(alternateJSONSuggestEngineData),
+    },
   ]);
 });
 
 
 // Begin tests
 
 add_task(async function simple_no_result_callback() {
   await new Promise(resolve => {
@@ -121,16 +132,27 @@ add_task(async function simple_remote_no
   Assert.equal(result.term, "mo");
   Assert.equal(result.local.length, 0);
   Assert.equal(result.remote.length, 3);
   Assert.equal(result.remote[0], "Mozilla");
   Assert.equal(result.remote[1], "modern");
   Assert.equal(result.remote[2], "mom");
 });
 
+add_task(async function simple_remote_no_local_result_alternative_type() {
+  let controller = new SearchSuggestionController();
+  let result = await controller.fetch("mo", false, alternateJSONEngine);
+  Assert.equal(result.term, "mo");
+  Assert.equal(result.local.length, 0);
+  Assert.equal(result.remote.length, 3);
+  Assert.equal(result.remote[0], "Mozilla");
+  Assert.equal(result.remote[1], "modern");
+  Assert.equal(result.remote[2], "mom");
+});
+
 add_task(async function remote_term_case_mismatch() {
   let controller = new SearchSuggestionController();
   let result = await controller.fetch("Query Case Mismatch", false, getEngine);
   Assert.equal(result.term, "Query Case Mismatch");
   Assert.equal(result.remote.length, 1);
   Assert.equal(result.remote[0], "Query Case Mismatch");
 });