diff --git a/lib/filter.js b/lib/filter.js
index 7eeb78147..bb104d5e4 100644
--- a/lib/filter.js
+++ b/lib/filter.js
@@ -17,7 +17,7 @@ function setProp(obj, keyNesting, val) {
         }
         currentObj = currentObj[nestedKeys[i]];
     }
-    currentObj[nestedKeys.length - 1] = val;
+    currentObj[nestedKeys[nestedKeys.length - 1]] = val;
 }
 
 /**
@@ -25,29 +25,29 @@ function setProp(obj, keyNesting, val) {
  * @constructor
  * @param {string} userId The user ID for this filter.
  * @param {string=} filterId The filter ID if known.
+ * @prop {string} userId The user ID of the filter
+ * @prop {?string} filterId The filter ID
  */
 function Filter(userId, filterId) {
     this.userId = userId;
     this.filterId = filterId;
-    this.body = {
-        event_format: "client"
-    };
+    this.definition = {};
 }
 
 /**
  * Get the JSON body of the filter.
- * @return {Object} The JSON body
+ * @return {Object} The filter definition
  */
-Filter.prototype.getBody = function() {
-    return this.body;
+Filter.prototype.getDefinition = function() {
+    return this.definition;
 };
 
 /**
  * Set the JSON body of the filter
- * @param {Object} body
+ * @param {Object} body The filter definition
  */
-Filter.prototype.setBody = function(body) {
-    this.body = body;
+Filter.prototype.setDefinition = function(definition) {
+    this.definition = definition;
 };
 
 /**
@@ -55,7 +55,7 @@ Filter.prototype.setBody = function(body) {
  * @param {Number} limit The max number of events to return for each room.
  */
 Filter.prototype.setTimelineLimit = function(limit) {
-    setProp(this.body, "room.timeline.limit", limit);
+    setProp(this.definition, "room.timeline.limit", limit);
 };
 
 /**
@@ -68,7 +68,7 @@ Filter.prototype.setTimelineLimit = function(limit) {
  */
 Filter.fromJson = function(userId, filterId, jsonObj) {
     var filter = new Filter(userId, filterId);
-    filter.setBody(jsonObj);
+    filter.setDefinition(jsonObj);
     return filter;
 };
 
diff --git a/lib/matrix.js b/lib/matrix.js
index 6f9b9bfe7..f150f7e76 100644
--- a/lib/matrix.js
+++ b/lib/matrix.js
@@ -34,6 +34,7 @@ module.exports.CRYPTO_ENABLED = require("./client").CRYPTO_ENABLED;
 module.exports.ContentRepo = require("./content-repo");
 /** The {@link module:filter~Filter|Filter} class. */
 module.exports.Filter = require("./filter");
+
 /**
  * Create a new Matrix Call.
  * @function
diff --git a/spec/unit/filter.spec.js b/spec/unit/filter.spec.js
new file mode 100644
index 000000000..e9c62f588
--- /dev/null
+++ b/spec/unit/filter.spec.js
@@ -0,0 +1,50 @@
+"use strict";
+var sdk = require("../..");
+var Filter = sdk.Filter;
+var utils = require("../test-utils");
+
+describe("Filter", function() {
+    var filterId = "f1lt3ring15g00d4ursoul";
+    var userId = "@sir_arthur_david:humming.tiger";
+    var filter;
+
+    beforeEach(function() {
+        utils.beforeEach(this);
+        filter = new Filter(userId);
+    });
+
+    describe("fromJson", function() {
+        it("create a new Filter from the provided values", function() {
+            var definition = {
+                event_fields: ["type", "content"]
+            };
+            var f = Filter.fromJson(userId, filterId, definition);
+            expect(f.getDefinition()).toEqual(definition);
+            expect(f.userId).toEqual(userId);
+            expect(f.filterId).toEqual(filterId);
+        });
+    });
+
+    describe("setTimelineLimit", function() {
+        it("should set room.timeline.limit of the filter definition", function() {
+            filter.setTimelineLimit(10);
+            expect(filter.getDefinition()).toEqual({
+                room: {
+                    timeline: {
+                        limit: 10
+                    }
+                }
+            });
+        });
+    });
+
+    describe("setDefinition/getDefinition", function() {
+        it("should set and get the filter body", function() {
+            var definition = {
+                event_format: "client"
+            };
+            filter.setDefinition(definition);
+            expect(filter.getDefinition()).toEqual(definition);
+        });
+    });
+});