diff --git a/Signal/src/ViewControllers/DebugUI/DebugUIMessagesAssetLoader.m b/Signal/src/ViewControllers/DebugUI/DebugUIMessagesAssetLoader.m
index ce959d113..2d7240764 100644
--- a/Signal/src/ViewControllers/DebugUI/DebugUIMessagesAssetLoader.m
+++ b/Signal/src/ViewControllers/DebugUI/DebugUIMessagesAssetLoader.m
@@ -371,7 +371,7 @@ NS_ASSUME_NONNULL_BEGIN
     dispatch_once(&onceToken, ^{
         instance = [DebugUIMessagesAssetLoader
             fakeAssetLoaderWithUrl:@"https://s3.amazonaws.com/ows-data/example_attachment_media/random-jpg.JPG"
-                          mimeType:@"image/jpeg"];
+                          mimeType:OWSMimeTypeImageJpeg];
     });
     return instance;
 }
diff --git a/SignalServiceKit/src/Messages/Attachments/TSAttachmentStream.m b/SignalServiceKit/src/Messages/Attachments/TSAttachmentStream.m
index fdddb64d0..1797b3215 100644
--- a/SignalServiceKit/src/Messages/Attachments/TSAttachmentStream.m
+++ b/SignalServiceKit/src/Messages/Attachments/TSAttachmentStream.m
@@ -688,7 +688,7 @@ NS_ASSUME_NONNULL_BEGIN
     // Copy the thumbnail to a new attachment.
     NSString *thumbnailName = [NSString stringWithFormat:@"quoted-thumbnail-%@", self.sourceFilename];
     TSAttachmentStream *thumbnailAttachment =
-        [[TSAttachmentStream alloc] initWithContentType:@"image/jpeg"
+        [[TSAttachmentStream alloc] initWithContentType:OWSMimeTypeImageJpeg
                                               byteCount:(uint32_t)thumbnailData.length
                                          sourceFilename:thumbnailName];
 
diff --git a/SignalServiceKit/src/Messages/OWSMessageSender.m b/SignalServiceKit/src/Messages/OWSMessageSender.m
index 5e9afd799..ff0b1cd83 100644
--- a/SignalServiceKit/src/Messages/OWSMessageSender.m
+++ b/SignalServiceKit/src/Messages/OWSMessageSender.m
@@ -5,12 +5,9 @@
 #import "OWSMessageSender.h"
 #import "AppContext.h"
 #import "ContactsUpdater.h"
-#import "Cryptography.h"
-#import "MIMETypeUtil.h"
 #import "NSData+keyVersionByte.h"
 #import "NSData+messagePadding.h"
 #import "NSError+MessageSending.h"
-#import "NSNotificationCenter+OWS.h"
 #import "OWSBackgroundTask.h"
 #import "OWSBlockingManager.h"
 #import "OWSDevice.h"
@@ -41,7 +38,6 @@
 #import "TSPreKeyManager.h"
 #import "TSQuotedMessage.h"
 #import "TSThread.h"
-#import "TextSecureKitEnv.h"
 #import "Threading.h"
 #import <AxolotlKit/AxolotlExceptions.h>
 #import <AxolotlKit/CipherMessage.h>
diff --git a/SignalServiceKit/src/Network/API/OWSUploadOperation.m b/SignalServiceKit/src/Network/API/OWSUploadOperation.m
index 58a649987..1789f2aeb 100644
--- a/SignalServiceKit/src/Network/API/OWSUploadOperation.m
+++ b/SignalServiceKit/src/Network/API/OWSUploadOperation.m
@@ -181,7 +181,6 @@ static const CGFloat kAttachmentUploadProgressTheta = 0.001f;
                                          }];
 }
 
-
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/SignalServiceKit/src/Util/OWSOperation.h b/SignalServiceKit/src/Util/OWSOperation.h
index 66b3dcaf6..102f46631 100644
--- a/SignalServiceKit/src/Util/OWSOperation.h
+++ b/SignalServiceKit/src/Util/OWSOperation.h
@@ -45,17 +45,18 @@ typedef NS_ENUM(NSInteger, OWSOperationState) {
 
 // Complete the operation successfully.
 // Should be called at most once per operation instance.
+// You must ensure that `run` cannot fail after calling `reportSuccess`.
 - (void)reportSuccess;
 
-// To avoid retry, report an error with `error.isFatal = YES`
-// otherwise the operation will retry if possible.
-// Should be called at most once per `run`, and you should
-// ensure that `run` cannot succeed after calling `reportError`
-// e.g. generally:
+// Should be called at most once per `run`.
+// You must ensure that `run` cannot succeed after calling `reportError`, e.g. generally you'll write something like
+// this:
 //
 //     [self reportError:someError];
 //     return;
 //
+// If the error is terminal, and you want to avoid retry, report an error with `error.isFatal = YES` otherwise the
+// operation will retry if possible.
 - (void)reportError:(NSError *)error;
 
 @end