diff --git a/src/Messages/OWSMessageSender.m b/src/Messages/OWSMessageSender.m
index ac1f25f3d..6c894f75b 100644
--- a/src/Messages/OWSMessageSender.m
+++ b/src/Messages/OWSMessageSender.m
@@ -483,6 +483,11 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
             };
 
             switch (statuscode) {
+                case 401: {
+                    DDLogWarn(@"%@ Unable to send due to invalid credentials. Did the user's client get de-authed by registering elsewhere?", self.tag);
+                    NSError *error = OWSErrorWithCodeDescription(OWSErrorCodeSignalServiceFailure, NSLocalizedString(@"ERROR_DESCRIPTION_SENDING_UNAUTHORIZED", @"Error message when attempting to send message"));
+                    return failureHandler(error);
+                }
                 case 404: {
                     [self unregisteredRecipient:recipient message:message thread:thread];
                     NSError *error = OWSErrorMakeNoSuchSignalRecipientError();
diff --git a/src/Util/OWSError.h b/src/Util/OWSError.h
index 9e921487c..897b020f9 100644
--- a/src/Util/OWSError.h
+++ b/src/Util/OWSError.h
@@ -14,6 +14,7 @@ typedef NS_ENUM(NSInteger, OWSErrorCode) {
     OWSErrorCodeUntrustedIdentityKey = 25,
     OWSErrorCodeFailedToSendOutgoingMessage = 30,
     OWSErrorCodeFailedToDecryptMessage = 100,
+    OWSErrorCodeSignalServiceFailure = 1001,
     OWSErrorCodeUserError = 2001,
 };