diff --git a/spec/TestClient.js b/spec/TestClient.js
index 29b443f4a44..a3d2dcb8a4e 100644
--- a/spec/TestClient.js
+++ b/spec/TestClient.js
@@ -185,7 +185,7 @@ TestClient.prototype.expectKeyQuery = function(response) {
         200, (path, content) => {
             Object.keys(response.device_keys).forEach((userId) => {
                 expect(content.device_keys[userId]).toEqual(
-                    {},
+                    [],
                     "Expected key query for " + userId + ", got " +
                     Object.keys(content.device_keys),
                 );
diff --git a/spec/integ/matrix-client-crypto.spec.js b/spec/integ/matrix-client-crypto.spec.js
index 8fe97ff2103..3ca72c32034 100644
--- a/spec/integ/matrix-client-crypto.spec.js
+++ b/spec/integ/matrix-client-crypto.spec.js
@@ -70,7 +70,7 @@ function expectAliQueryKeys() {
     aliTestClient.httpBackend.when("POST", "/keys/query")
             .respond(200, function(path, content) {
         expect(content.device_keys[bobUserId]).toEqual(
-            {},
+            [],
             "Expected Alice to key query for " + bobUserId + ", got " +
             Object.keys(content.device_keys),
         );
@@ -98,7 +98,7 @@ function expectBobQueryKeys() {
         "POST", "/keys/query",
     ).respond(200, function(path, content) {
         expect(content.device_keys[aliUserId]).toEqual(
-            {},
+            [],
             "Expected Bob to key query for " + aliUserId + ", got " +
             Object.keys(content.device_keys),
         );
diff --git a/spec/integ/matrix-client-methods.spec.js b/spec/integ/matrix-client-methods.spec.js
index be241c9121b..b79fd26d716 100644
--- a/spec/integ/matrix-client-methods.spec.js
+++ b/spec/integ/matrix-client-methods.spec.js
@@ -347,8 +347,8 @@ describe("MatrixClient", function() {
 
             httpBackend.when("POST", "/keys/query").check(function(req) {
                 expect(req.data).toEqual({device_keys: {
-                    'boris': {},
-                    'chaz': {},
+                    'boris': [],
+                    'chaz': [],
                 }});
             }).respond(200, {
                 device_keys: {
diff --git a/src/base-apis.js b/src/base-apis.js
index 6491b1510d5..ce74ce8edd0 100644
--- a/src/base-apis.js
+++ b/src/base-apis.js
@@ -1757,7 +1757,7 @@ MatrixBaseApis.prototype.downloadKeysForUsers = function(userIds, opts) {
         content.token = opts.token;
     }
     userIds.forEach((u) => {
-        content.device_keys[u] = {};
+        content.device_keys[u] = [];
     });
 
     return this._http.authedRequest(undefined, "POST", "/keys/query", undefined, content);