diff --git a/SignalServiceKit/src/Util/NSTimer+OWS.h b/SignalServiceKit/src/Util/NSTimer+OWS.h
index e301b39b0..c530f209e 100644
--- a/SignalServiceKit/src/Util/NSTimer+OWS.h
+++ b/SignalServiceKit/src/Util/NSTimer+OWS.h
@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 NS_ASSUME_NONNULL_BEGIN
diff --git a/SignalServiceKit/src/Util/NSTimer+OWS.m b/SignalServiceKit/src/Util/NSTimer+OWS.m
index a2f02f2a4..12eb39175 100644
--- a/SignalServiceKit/src/Util/NSTimer+OWS.m
+++ b/SignalServiceKit/src/Util/NSTimer+OWS.m
@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 #import "NSTimer+OWS.h"
diff --git a/SignalServiceKit/src/Util/OWSOperation.m b/SignalServiceKit/src/Util/OWSOperation.m
index e3455a5f7..444d9c886 100644
--- a/SignalServiceKit/src/Util/OWSOperation.m
+++ b/SignalServiceKit/src/Util/OWSOperation.m
@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 #import "OWSOperation.h"
@@ -18,8 +18,9 @@ NSString *const OWSOperationKeyIsFinished = @"isFinished";
 @property (nullable) NSError *failingError;
 @property (atomic) OWSOperationState operationState;
 @property (nonatomic) OWSBackgroundTask *backgroundTask;
+
+// This property should only be accessed on the main queue.
 @property (nonatomic) NSTimer *_Nullable retryTimer;
-@property (nonatomic, readonly) dispatch_queue_t retryTimerSerialQueue;
 
 @end
 
@@ -34,7 +35,6 @@ NSString *const OWSOperationKeyIsFinished = @"isFinished";
 
     _operationState = OWSOperationStateNew;
     _backgroundTask = [OWSBackgroundTask backgroundTaskWithLabel:self.logTag];
-    _retryTimerSerialQueue = dispatch_queue_create("SignalServiceKit.OWSOperation.retryTimer", DISPATCH_QUEUE_SERIAL);
 
     // Operations are not retryable by default.
     _remainingRetries = 0;
@@ -131,18 +131,19 @@ NSString *const OWSOperationKeyIsFinished = @"isFinished";
 
 - (void)runAnyQueuedRetry
 {
-    __block NSTimer *_Nullable retryTimer;
-    dispatch_sync(self.retryTimerSerialQueue, ^{
-        retryTimer = self.retryTimer;
+    dispatch_async(dispatch_get_main_queue(), ^{
+        NSTimer *_Nullable retryTimer = self.retryTimer;
         self.retryTimer = nil;
         [retryTimer invalidate];
-    });
 
-    if (retryTimer != nil) {
-        [self run];
-    } else {
-        OWSLogVerbose(@"not re-running since operation is already running.");
-    }
+        if (retryTimer != nil) {
+            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+                [self run];
+            });
+        } else {
+            OWSLogVerbose(@"not re-running since operation is already running.");
+        }
+    });
 }
 
 #pragma mark - Public Methods
@@ -190,9 +191,17 @@ NSString *const OWSOperationKeyIsFinished = @"isFinished";
 
     self.remainingRetries--;
 
-    dispatch_sync(self.retryTimerSerialQueue, ^{
+    dispatch_async(dispatch_get_main_queue(), ^{
         OWSAssertDebug(self.retryTimer == nil);
         [self.retryTimer invalidate];
+
+        // The `scheduledTimerWith*` methods add the timer to the current thread's RunLoop.
+        // Since Operations typically run on a background thread, that would mean the background
+        // thread's RunLoop. However, the OS can spin down background threads if there's no work
+        // being done, so we run the risk of the timer's RunLoop being deallocated before it's
+        // fired.
+        //
+        // To ensure the timer's thread sticks around, we schedule it while on the main RunLoop.
         self.retryTimer = [NSTimer weakScheduledTimerWithTimeInterval:self.retryInterval
                                                                target:self
                                                              selector:@selector(runAnyQueuedRetry)