diff --git a/chrome/content/zotero/xpcom/sync/syncAPIClient.js b/chrome/content/zotero/xpcom/sync/syncAPIClient.js
index 911a5ae3e..b56439e38 100644
--- a/chrome/content/zotero/xpcom/sync/syncAPIClient.js
+++ b/chrome/content/zotero/xpcom/sync/syncAPIClient.js
@@ -587,7 +587,7 @@ Zotero.Sync.APIClient.prototype = {
 									this.failureDelayIntervals, 60 * 60 * 1000
 								);
 							}
-							let keepGoing = yield failureDelayGenerator.next();
+							let keepGoing = yield failureDelayGenerator.next().value;
 							if (!keepGoing) {
 								Zotero.logError("Failed too many times");
 								throw lastError;
diff --git a/chrome/content/zotero/xpcom/utilities_internal.js b/chrome/content/zotero/xpcom/utilities_internal.js
index 51c08986b..b726d3b8f 100644
--- a/chrome/content/zotero/xpcom/utilities_internal.js
+++ b/chrome/content/zotero/xpcom/utilities_internal.js
@@ -461,25 +461,23 @@ Zotero.Utilities.Internal = {
 	 *                              promise will return false. Before maxTime has elapsed, or if
 	 *                              maxTime isn't specified, the promises will yield true.
 	 */
-	"delayGenerator": function (intervals, maxTime) {
+	"delayGenerator": function* (intervals, maxTime) {
 		var totalTime = 0;
-		var lastInterval = intervals[intervals.length - 1];
+		var last = false;
 		while (true) {
 			let interval = intervals.shift();
 			if (interval) {
-				delay = lastInterval = interval;
+				delay = interval;
 			}
-			else if (infinite) {
-				delay = lastInterval;
-			}
-			else {
-				break;
+			
+			if (maxTime && (totalTime + delay) > maxTime) {
+				yield Zotero.Promise.resolve(false);
 			}
 			
 			totalTime += delay;
 			
 			Zotero.debug("Delaying " + delay + " ms");
-			yield Zotero.Promise.delay(delay).return(!maxTime || totalTime <= maxTime);
+			yield Zotero.Promise.delay(delay).return(true);
 		}
 	},
 	
diff --git a/test/tests/utilities_internalTest.js b/test/tests/utilities_internalTest.js
index 7ff552908..c76ead75e 100644
--- a/test/tests/utilities_internalTest.js
+++ b/test/tests/utilities_internalTest.js
@@ -10,4 +10,58 @@ describe("Zotero.Utilities.Internal", function () {
 			);
 		})
 	})
+	
+	
+	describe("#delayGenerator", function () {
+		var spy;
+		
+		before(function () {
+			spy = sinon.spy(Zotero.Promise, "delay");
+		});
+		
+		afterEach(function () {
+			spy.reset();
+		});
+		
+		after(function () {
+			spy.restore();
+		});
+		
+		it("should delay for given amounts of time without limit", function* () {
+			var intervals = [1, 2];
+			var gen = Zotero.Utilities.Internal.delayGenerator(intervals);
+			
+			// When intervals are exhausted, keep using last interval
+			var testIntervals = intervals.slice();
+			testIntervals.push(intervals[intervals.length - 1]);
+			
+			for (let i of testIntervals) {
+				let val = yield gen.next().value;
+				assert.isTrue(val);
+				assert.isTrue(spy.calledWith(i));
+				spy.reset();
+			}
+		});
+		
+		it("should return false when maxTime is reached", function* () {
+			var intervals = [5, 10];
+			var gen = Zotero.Utilities.Internal.delayGenerator(intervals, 30);
+			
+			// When intervals are exhausted, keep using last interval
+			var testIntervals = intervals.slice();
+			testIntervals.push(intervals[intervals.length - 1]);
+			
+			for (let i of testIntervals) {
+				let val = yield gen.next().value;
+				assert.isTrue(val);
+				assert.isTrue(spy.calledWith(i));
+				spy.reset();
+			}
+			
+			// Another interval would put us over maxTime, so return false immediately
+			let val = yield gen.next().value;
+			assert.isFalse(val);
+			assert.isFalse(spy.called);
+		});
+	})
 })