diff --git a/Signal/src/network/GiphyDownloader.swift b/Signal/src/network/GiphyDownloader.swift
index dc05f3b7b..d4b5e9ba8 100644
--- a/Signal/src/network/GiphyDownloader.swift
+++ b/Signal/src/network/GiphyDownloader.swift
@@ -802,7 +802,7 @@ extension URLSessionTask {
             return
         }
         guard let httpResponse = task.response as? HTTPURLResponse else {
-            Logger.error("\(TAG) missing or unexpected response: \(task.response)")
+            Logger.error("\(TAG) missing or unexpected response: \(String(describing: task.response))")
             segmentRequestDidFail(assetRequest:assetRequest, assetSegment:assetSegment)
             return
         }
diff --git a/SignalServiceKit/src/Account/TSPreKeyManager.m b/SignalServiceKit/src/Account/TSPreKeyManager.m
index b9ae9477d..50618e153 100644
--- a/SignalServiceKit/src/Account/TSPreKeyManager.m
+++ b/SignalServiceKit/src/Account/TSPreKeyManager.m
@@ -344,7 +344,7 @@ static const NSTimeInterval kSignedPreKeyUpdateFailureMaxFailureDuration = 10 *
     [self clearSignedPreKeyRecordsWithKeyId:currentSignedPrekeyId success:nil];
 }
 
-+ (void)clearSignedPreKeyRecordsWithKeyId:(NSNumber *)keyId success:(void (^_Nullable)())successHandler
++ (void)clearSignedPreKeyRecordsWithKeyId:(NSNumber *)keyId success:(void (^_Nullable)(void))successHandler
 {
     if (!keyId) {
         OWSFail(@"%@ Ignoring request to clear signed preKeys since no keyId was specified", self.logTag);
diff --git a/SignalServiceKit/src/Messages/Attachments/OWSAttachmentsProcessor.m b/SignalServiceKit/src/Messages/Attachments/OWSAttachmentsProcessor.m
index b96cb4931..42af6c758 100644
--- a/SignalServiceKit/src/Messages/Attachments/OWSAttachmentsProcessor.m
+++ b/SignalServiceKit/src/Messages/Attachments/OWSAttachmentsProcessor.m
@@ -305,7 +305,7 @@ static const CGFloat kAttachmentDownloadProgressTheta = 0.001f;
                 return;
             }
 
-            void (^abortDownload)() = ^{
+            void (^abortDownload)(void) = ^{
                 OWSFail(@"%@ Download aborted.", self.logTag);
                 [task cancel];
             };
diff --git a/SignalServiceKit/src/Messages/OWSMessageDecrypter.h b/SignalServiceKit/src/Messages/OWSMessageDecrypter.h
index b3dcfce76..8ac758a65 100644
--- a/SignalServiceKit/src/Messages/OWSMessageDecrypter.h
+++ b/SignalServiceKit/src/Messages/OWSMessageDecrypter.h
@@ -9,7 +9,7 @@ NS_ASSUME_NONNULL_BEGIN
 @class OWSSignalServiceProtosEnvelope;
 
 typedef void (^DecryptSuccessBlock)(NSData *_Nullable plaintextData);
-typedef void (^DecryptFailureBlock)();
+typedef void (^DecryptFailureBlock)(void);
 
 @interface OWSMessageDecrypter : OWSMessageHandler
 
diff --git a/SignalServiceKit/src/Network/API/OWSUploadingService.m b/SignalServiceKit/src/Network/API/OWSUploadingService.m
index 122537257..03a203d3d 100644
--- a/SignalServiceKit/src/Network/API/OWSUploadingService.m
+++ b/SignalServiceKit/src/Network/API/OWSUploadingService.m
@@ -47,7 +47,7 @@ static const CGFloat kAttachmentUploadProgressTheta = 0.001f;
                        success:(void (^)(void))successHandler
                        failure:(RetryableFailureHandler)failureHandler
 {
-    void (^successHandlerWrapper)() = ^{
+    void (^successHandlerWrapper)(void) = ^{
         [self fireProgressNotification:1 attachmentId:attachmentStream.uniqueId];
 
         successHandler();
@@ -61,7 +61,7 @@ static const CGFloat kAttachmentUploadProgressTheta = 0.001f;
 
     if (attachmentStream.serverId) {
         DDLogDebug(@"%@ Attachment previously uploaded.", self.logTag);
-        successHandlerWrapper(outgoingMessage);
+        successHandlerWrapper();
         return;
     }
 
diff --git a/SignalServiceKit/src/Network/API/Requests/OWSDeleteDeviceRequest.h b/SignalServiceKit/src/Network/API/Requests/OWSDeleteDeviceRequest.h
index 044cd057e..f4ba003c9 100644
--- a/SignalServiceKit/src/Network/API/Requests/OWSDeleteDeviceRequest.h
+++ b/SignalServiceKit/src/Network/API/Requests/OWSDeleteDeviceRequest.h
@@ -1,4 +1,6 @@
-//  Copyright © 2016 Open Whisper Systems. All rights reserved.
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
 
 #import "TSRequest.h"
 
@@ -12,4 +14,4 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-NS_ASSUME_NONNULL_END
\ No newline at end of file
+NS_ASSUME_NONNULL_END
diff --git a/SignalServiceKit/src/Network/API/Requests/TSProfileAvatarUploadFormRequest.h b/SignalServiceKit/src/Network/API/Requests/TSProfileAvatarUploadFormRequest.h
index 5e80c51ec..8a32f12cd 100644
--- a/SignalServiceKit/src/Network/API/Requests/TSProfileAvatarUploadFormRequest.h
+++ b/SignalServiceKit/src/Network/API/Requests/TSProfileAvatarUploadFormRequest.h
@@ -8,7 +8,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface TSProfileAvatarUploadFormRequest : TSRequest
 
-- (nullable instancetype)init;
+- (instancetype)init;
 
 @end
 
diff --git a/SignalServiceKit/src/Network/API/Requests/TSProfileAvatarUploadFormRequest.m b/SignalServiceKit/src/Network/API/Requests/TSProfileAvatarUploadFormRequest.m
index bb820c210..0b0972a46 100644
--- a/SignalServiceKit/src/Network/API/Requests/TSProfileAvatarUploadFormRequest.m
+++ b/SignalServiceKit/src/Network/API/Requests/TSProfileAvatarUploadFormRequest.m
@@ -9,7 +9,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @implementation TSProfileAvatarUploadFormRequest
 
-- (nullable instancetype)init
+- (instancetype)init
 {
     self = [super initWithURL:[NSURL URLWithString:textSecureProfileAvatarFormAPI]];
 
diff --git a/SignalServiceKit/src/Storage/OWSOrphanedDataCleaner.h b/SignalServiceKit/src/Storage/OWSOrphanedDataCleaner.h
index 960256a10..1b4f8fb2f 100644
--- a/SignalServiceKit/src/Storage/OWSOrphanedDataCleaner.h
+++ b/SignalServiceKit/src/Storage/OWSOrphanedDataCleaner.h
@@ -19,7 +19,7 @@ NS_ASSUME_NONNULL_BEGIN
 + (void)auditAsync;
 
 // completion, if present, will be invoked on the main thread.
-+ (void)auditAndCleanupAsync:(void (^_Nullable)())completion;
++ (void)auditAndCleanupAsync:(void (^_Nullable)(void))completion;
 
 + (NSSet<NSString *> *)filePathsInAttachmentsFolder;
 
diff --git a/SignalServiceKit/src/Storage/OWSOrphanedDataCleaner.m b/SignalServiceKit/src/Storage/OWSOrphanedDataCleaner.m
index 35fdfc30e..4d05cf886 100644
--- a/SignalServiceKit/src/Storage/OWSOrphanedDataCleaner.m
+++ b/SignalServiceKit/src/Storage/OWSOrphanedDataCleaner.m
@@ -29,7 +29,7 @@ NS_ASSUME_NONNULL_BEGIN
     });
 }
 
-+ (void)auditAndCleanupAsync:(void (^_Nullable)())completion
++ (void)auditAndCleanupAsync:(void (^_Nullable)(void))completion
 {
     dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
         [OWSOrphanedDataCleaner auditAndCleanup:YES completion:completion];
@@ -47,7 +47,7 @@ NS_ASSUME_NONNULL_BEGIN
 //   They can't be cleaned up - we don't want to delete the TSAttachmentStream or
 //   its corresponding message.  Better that the broken message shows up in the
 //   conversation view.
-+ (void)auditAndCleanup:(BOOL)shouldCleanup completion:(void (^_Nullable)())completion
++ (void)auditAndCleanup:(BOOL)shouldCleanup completion:(void (^_Nullable)(void))completion
 {
     NSSet<NSString *> *diskFilePaths = [self filePathsInAttachmentsFolder];
     long long totalFileSize = [self fileSizeOfFilePaths:diskFilePaths.allObjects];
diff --git a/SignalServiceKit/src/Storage/TSStorageManager.h b/SignalServiceKit/src/Storage/TSStorageManager.h
index 38ce97988..753408f8e 100644
--- a/SignalServiceKit/src/Storage/TSStorageManager.h
+++ b/SignalServiceKit/src/Storage/TSStorageManager.h
@@ -34,7 +34,7 @@ NS_ASSUME_NONNULL_BEGIN
  * Specifically, these migration should not depend on or affect the data
  * of any database view.
  */
-- (void)setupDatabaseWithSafeBlockingMigrations:(void (^_Nonnull)())safeBlockingMigrationsBlock;
+- (void)setupDatabaseWithSafeBlockingMigrations:(void (^_Nonnull)(void))safeBlockingMigrationsBlock;
 
 - (void)deleteThreadsAndMessages;
 - (void)resetSignalStorage;
diff --git a/SignalServiceKit/src/Storage/TSStorageManager.m b/SignalServiceKit/src/Storage/TSStorageManager.m
index 207973206..503226efd 100644
--- a/SignalServiceKit/src/Storage/TSStorageManager.m
+++ b/SignalServiceKit/src/Storage/TSStorageManager.m
@@ -307,7 +307,7 @@ void setDatabaseInitialized()
     };
 }
 
-- (void)setupDatabaseWithSafeBlockingMigrations:(void (^_Nonnull)())safeBlockingMigrationsBlock
+- (void)setupDatabaseWithSafeBlockingMigrations:(void (^_Nonnull)(void))safeBlockingMigrationsBlock
 {
     // Synchronously register extensions which are essential for views.
     [TSDatabaseView registerCrossProcessNotifier];
diff --git a/SignalServiceKit/src/Util/OWSAnalytics.h b/SignalServiceKit/src/Util/OWSAnalytics.h
index 840f6a8cd..9cb59ed4d 100755
--- a/SignalServiceKit/src/Util/OWSAnalytics.h
+++ b/SignalServiceKit/src/Util/OWSAnalytics.h
@@ -44,7 +44,7 @@ typedef NS_ENUM(NSUInteger, OWSAnalyticsSeverity) {
 
 @end
 
-typedef NSDictionary<NSString *, id> *_Nonnull (^OWSProdAssertParametersBlock)();
+typedef NSDictionary<NSString *, id> *_Nonnull (^OWSProdAssertParametersBlock)(void);
 
 // These methods should be used to assert errors for which we want to fire analytics events.
 //
diff --git a/SignalServiceKit/src/Util/OWSAnalytics.m b/SignalServiceKit/src/Util/OWSAnalytics.m
index 8e8662474..28ed30e25 100755
--- a/SignalServiceKit/src/Util/OWSAnalytics.m
+++ b/SignalServiceKit/src/Util/OWSAnalytics.m
@@ -222,8 +222,8 @@ NSString *NSStringForOWSAnalyticsSeverity(OWSAnalyticsSeverity severity)
 
 - (void)submitEvent:(NSDictionary *)eventDictionary
            eventKey:(NSString *)eventKey
-            success:(void (^_Nonnull)())successBlock
-            failure:(void (^_Nonnull)())failureBlock
+            success:(void (^_Nonnull)(void))successBlock
+            failure:(void (^_Nonnull)(void))failureBlock
 {
     OWSAssert(eventDictionary);
     OWSAssert(eventKey);
@@ -311,7 +311,7 @@ NSString *NSStringForOWSAnalyticsSeverity(OWSAnalyticsSeverity severity)
         return;
     }
 
-    void (^addEvent)() = ^{
+    void (^addEvent)(void) = ^{
         // Add super properties.
         NSMutableDictionary *eventProperties = (properties ? [properties mutableCopy] : [NSMutableDictionary new]);
         [eventProperties addEntriesFromDictionary:self.eventSuperProperties];
diff --git a/SignalServiceKit/src/Util/OWSDispatch.h b/SignalServiceKit/src/Util/OWSDispatch.h
index e31eebc35..9a3c9d4e5 100644
--- a/SignalServiceKit/src/Util/OWSDispatch.h
+++ b/SignalServiceKit/src/Util/OWSDispatch.h
@@ -24,6 +24,6 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-void AssertIsOnMainThread();
+void AssertIsOnMainThread(void);
 
 NS_ASSUME_NONNULL_END
diff --git a/SignalServiceKit/src/Util/OWSError.h b/SignalServiceKit/src/Util/OWSError.h
index 834497c88..6fbe95752 100644
--- a/SignalServiceKit/src/Util/OWSError.h
+++ b/SignalServiceKit/src/Util/OWSError.h
@@ -30,12 +30,12 @@ typedef NS_ENUM(NSInteger, OWSErrorCode) {
 };
 
 extern NSError *OWSErrorWithCodeDescription(OWSErrorCode code, NSString *description);
-extern NSError *OWSErrorMakeUnableToProcessServerResponseError();
-extern NSError *OWSErrorMakeFailedToSendOutgoingMessageError();
-extern NSError *OWSErrorMakeNoSuchSignalRecipientError();
-extern NSError *OWSErrorMakeAssertionError();
-extern NSError *OWSErrorMakeMessageSendDisabledDueToPreKeyUpdateFailuresError();
-extern NSError *OWSErrorMakeMessageSendFailedToBlockListError();
-extern NSError *OWSErrorMakeWriteAttachmentDataError();
+extern NSError *OWSErrorMakeUnableToProcessServerResponseError(void);
+extern NSError *OWSErrorMakeFailedToSendOutgoingMessageError(void);
+extern NSError *OWSErrorMakeNoSuchSignalRecipientError(void);
+extern NSError *OWSErrorMakeAssertionError(void);
+extern NSError *OWSErrorMakeMessageSendDisabledDueToPreKeyUpdateFailuresError(void);
+extern NSError *OWSErrorMakeMessageSendFailedToBlockListError(void);
+extern NSError *OWSErrorMakeWriteAttachmentDataError(void);
 
 NS_ASSUME_NONNULL_END