diff --git a/spec/unit/matrix-client.spec.ts b/spec/unit/matrix-client.spec.ts
index 702c22c05f4..d1d0bf5baaf 100644
--- a/spec/unit/matrix-client.spec.ts
+++ b/spec/unit/matrix-client.spec.ts
@@ -427,7 +427,7 @@ describe("MatrixClient", function() {
                 }
             });
         });
-        await client.startClient();
+        await client.startClient({ filter });
         await syncPromise;
     });
 
diff --git a/spec/unit/utils.spec.ts b/spec/unit/utils.spec.ts
index 36ad9e164bc..be30890edea 100644
--- a/spec/unit/utils.spec.ts
+++ b/spec/unit/utils.spec.ts
@@ -152,6 +152,9 @@ describe("utils", function() {
             assert.isTrue(utils.deepCompare({ a: 1, b: 2 }, { a: 1, b: 2 }));
             assert.isTrue(utils.deepCompare({ a: 1, b: 2 }, { b: 2, a: 1 }));
             assert.isFalse(utils.deepCompare({ a: 1, b: 2 }, { a: 1, b: 3 }));
+            assert.isFalse(utils.deepCompare({ a: 1, b: 2 }, { a: 1 }));
+            assert.isFalse(utils.deepCompare({ a: 1 }, { a: 1, b: 2 }));
+            assert.isFalse(utils.deepCompare({ a: 1 }, { b: 1 }));
 
             assert.isTrue(utils.deepCompare({
                 1: { name: "mhc", age: 28 },
diff --git a/src/sync.ts b/src/sync.ts
index 430e0260229..396b5ba45d3 100644
--- a/src/sync.ts
+++ b/src/sync.ts
@@ -102,7 +102,7 @@ const MSC2716_ROOM_VERSIONS = [
 function getFilterName(userId: string, suffix?: string): string {
     // scope this on the user ID because people may login on many accounts
     // and they all need to be stored!
-    return `FILTER_SYNC_${userId}` + suffix ? "_" + suffix : "";
+    return `FILTER_SYNC_${userId}` + (suffix ? "_" + suffix : "");
 }
 
 function debuglog(...params) {
diff --git a/src/utils.ts b/src/utils.ts
index f9c087fd93a..ffb438d5b90 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -238,33 +238,24 @@ export function deepCompare(x: any, y: any): boolean {
             }
         }
     } else {
-        // disable jshint "The body of a for in should be wrapped in an if
-        // statement"
-        /* jshint -W089 */
-
         // check that all of y's direct keys are in x
-        let p;
-        for (p in y) {
+        for (const p in y) {
             if (y.hasOwnProperty(p) !== x.hasOwnProperty(p)) {
                 return false;
             }
         }
 
         // finally, compare each of x's keys with y
-        for (p in y) { // eslint-disable-line guard-for-in
-            if (y.hasOwnProperty(p) !== x.hasOwnProperty(p)) {
-                return false;
-            }
-            if (!deepCompare(x[p], y[p])) {
+        for (const p in x) {
+            if (y.hasOwnProperty(p) !== x.hasOwnProperty(p) || !deepCompare(x[p], y[p])) {
                 return false;
             }
         }
     }
-    /* jshint +W089 */
     return true;
 }
 
-// Dev note: This returns a tuple, but jsdoc doesn't like that. https://github.com/jsdoc/jsdoc/issues/1703
+// Dev note: This returns an array of tuples, but jsdoc doesn't like that. https://github.com/jsdoc/jsdoc/issues/1703
 /**
  * Creates an array of object properties/values (entries) then
  * sorts the result by key, recursively. The input object must