diff --git a/Signal/src/AppDelegate.m b/Signal/src/AppDelegate.m
index a50a7dd78..6748639f3 100644
--- a/Signal/src/AppDelegate.m
+++ b/Signal/src/AppDelegate.m
@@ -793,6 +793,9 @@ static NSString *const kURLHostVerifyPrefix             = @"verify";
     [AppVersion.instance appLaunchDidComplete];
 
     [self ensureRootViewController];
+
+    // If there were any messages in our local queue which we hadn't yet processed.
+    [[OWSMessageReceiver sharedInstance] handleAnyUnprocessedEnvelopesAsync];
 }
 
 - (void)ensureRootViewController
diff --git a/SignalServiceKit/src/Messages/OWSMessageReceiver.h b/SignalServiceKit/src/Messages/OWSMessageReceiver.h
index 6418f7b3c..5af585219 100644
--- a/SignalServiceKit/src/Messages/OWSMessageReceiver.h
+++ b/SignalServiceKit/src/Messages/OWSMessageReceiver.h
@@ -13,6 +13,7 @@ NS_ASSUME_NONNULL_BEGIN
 + (void)syncRegisterDatabaseExtension:(YapDatabase *)database;
 
 - (void)handleReceivedEnvelope:(OWSSignalServiceProtosEnvelope *)envelope;
+- (void)handleAnyUnprocessedEnvelopesAsync;
 
 @end
 
diff --git a/SignalServiceKit/src/Messages/OWSMessageReceiver.m b/SignalServiceKit/src/Messages/OWSMessageReceiver.m
index d144fb981..91e979ae8 100644
--- a/SignalServiceKit/src/Messages/OWSMessageReceiver.m
+++ b/SignalServiceKit/src/Messages/OWSMessageReceiver.m
@@ -186,6 +186,7 @@ NSString *const OWSMessageProcessingJobFinderExtensionGroup = @"OWSMessageProces
 
 @property (nonatomic, readonly) TSMessagesManager *messagesManager;
 @property (nonatomic, readonly) OWSMessageProcessingJobFinder *finder;
+@property (nonatomic) BOOL isDrainingQueue;
 
 - (instancetype)initWithMessagesManager:(TSMessagesManager *)messagesManager
                                  finder:(OWSMessageProcessingJobFinder *)finder NS_DESIGNATED_INITIALIZER;
@@ -207,6 +208,7 @@ NSString *const OWSMessageProcessingJobFinderExtensionGroup = @"OWSMessageProces
 
     _messagesManager = messagesManager;
     _finder = finder;
+    _isDrainingQueue = NO;
 
     return self;
 }
@@ -220,41 +222,43 @@ NSString *const OWSMessageProcessingJobFinderExtensionGroup = @"OWSMessageProces
 
 - (void)drainQueue
 {
-    dispatch_async(self.class.serialGCDQueue, ^{
-        OWSMessageProcessingJob *_Nullable job = [self.finder nextJob];
-        if (job == nil) {
-            DDLogVerbose(@"%@ Queue is drained", self.tag);
-            return;
-        }
-
-        [self processJob:job
-              completion:^{
-                  [self drainQueue];
-              }];
-    });
+    AssertIsOnMainThread();
+
+    if (self.isDrainingQueue) {
+        return;
+    }
+    self.isDrainingQueue = YES;
+
+    [self drainQueueWorkStep];
 }
 
-- (void)processJob:(OWSMessageProcessingJob *)job completion:(void (^)())completion
+- (void)drainQueueWorkStep
 {
-    dispatch_async(dispatch_get_main_queue(), ^{
-        [self.messagesManager processEnvelope:job.envelopeProto
-                                   completion:^{
-                                       [self.finder removeJobWithId:job.uniqueId];
-                                       completion();
-                                   }];
-    });
-}
+    AssertIsOnMainThread();
+
+    OWSMessageProcessingJob *_Nullable job = [self.finder nextJob];
+    if (job == nil) {
+        self.isDrainingQueue = NO;
+        DDLogVerbose(@"%@ Queue is drained", self.tag);
+        return;
+    }
 
-#pragma mark Helpers
+    [self processJob:job
+          completion:^{
+              DDLogVerbose(@"%@ completed job. %lu jobs left.",
+                  self.tag,
+                  (unsigned long)[OWSMessageProcessingJob numberOfKeysInCollection]);
+              [self drainQueueWorkStep];
+          }];
+}
 
-+ (dispatch_queue_t)serialGCDQueue
+- (void)processJob:(OWSMessageProcessingJob *)job completion:(void (^)())completion
 {
-    static dispatch_once_t onceToken;
-    static dispatch_queue_t queue;
-    dispatch_once(&onceToken, ^{
-        queue = dispatch_queue_create("org.whispersystems.signal.messageProcessingQueue", NULL);
-    });
-    return queue;
+    [self.messagesManager processEnvelope:job.envelopeProto
+                               completion:^{
+                                   [self.finder removeJobWithId:job.uniqueId];
+                                   completion();
+                               }];
 }
 
 #pragma mark Logging
@@ -331,6 +335,13 @@ NSString *const OWSMessageProcessingJobFinderExtensionGroup = @"OWSMessageProces
 
 #pragma mark - instance methods
 
+- (void)handleAnyUnprocessedEnvelopesAsync
+{
+    dispatch_async(dispatch_get_main_queue(), ^{
+        [self.processingQueue drainQueue];
+    });
+}
+
 - (void)handleReceivedEnvelope:(OWSSignalServiceProtosEnvelope *)envelope
 {
     // Drop any too-large messages on the floor. Well behaving clients should never send them.