diff --git a/Podfile b/Podfile
index 228be5bb6..e8031bb64 100644
--- a/Podfile
+++ b/Podfile
@@ -19,7 +19,7 @@ def shared_pods
   pod 'Curve25519Kit', git: 'https://github.com/signalapp/Curve25519Kit', testspecs: ["Tests"]
   # pod 'Curve25519Kit', path: '../Curve25519Kit', testspecs: ["Tests"]
   # TODO: Use public repo.
-  pod 'SignalMetadataKit', git: 'https://github.com/signalapp/SignalMetadataKit', testspecs: ["Tests"]
+  pod 'SignalMetadataKit', git: 'https://github.com/signalapp/SignalMetadataKit', testspecs: ["Tests"], branch: 'charlesmchen/discardSelfSentMessages'
   # pod 'SignalMetadataKit', path: '../SignalMetadataKit', testspecs: ["Tests"]
   pod 'SignalServiceKit', path: '.', testspecs: ["Tests"]
   pod 'GRKOpenSSLFramework', git: 'https://github.com/signalapp/GRKOpenSSLFramework'
diff --git a/Podfile.lock b/Podfile.lock
index d4cf61fc0..aaf2e22cf 100644
--- a/Podfile.lock
+++ b/Podfile.lock
@@ -196,8 +196,8 @@ DEPENDENCIES:
   - Reachability
   - SignalCoreKit (from `https://github.com/signalapp/SignalCoreKit.git`)
   - SignalCoreKit/Tests (from `https://github.com/signalapp/SignalCoreKit.git`)
-  - SignalMetadataKit (from `https://github.com/signalapp/SignalMetadataKit`)
-  - SignalMetadataKit/Tests (from `https://github.com/signalapp/SignalMetadataKit`)
+  - SignalMetadataKit (from `https://github.com/signalapp/SignalMetadataKit`, branch `charlesmchen/discardSelfSentMessages`)
+  - SignalMetadataKit/Tests (from `https://github.com/signalapp/SignalMetadataKit`, branch `charlesmchen/discardSelfSentMessages`)
   - SignalServiceKit (from `.`)
   - SignalServiceKit/Tests (from `.`)
   - SocketRocket (from `https://github.com/signalapp/SocketRocket.git`, branch `mkirk/handle-sec-err`)
@@ -233,6 +233,7 @@ EXTERNAL SOURCES:
   SignalCoreKit:
     :git: https://github.com/signalapp/SignalCoreKit.git
   SignalMetadataKit:
+    :branch: charlesmchen/discardSelfSentMessages
     :git: https://github.com/signalapp/SignalMetadataKit
   SignalServiceKit:
     :path: "."
@@ -263,7 +264,7 @@ CHECKOUT OPTIONS:
     :commit: ff0b95770520133b83a4bd7b26bc2c90b51abc4d
     :git: https://github.com/signalapp/SignalCoreKit.git
   SignalMetadataKit:
-    :commit: b0e664410dd3d709355bfdb9d464ae02644aeb74
+    :commit: 0ff4673181315f5bd7b883a87b783b5772f7b412
     :git: https://github.com/signalapp/SignalMetadataKit
   SocketRocket:
     :commit: 9f9563a83cd8960503074aa8de72206f83fb7a69
@@ -298,6 +299,6 @@ SPEC CHECKSUMS:
   YapDatabase: b418a4baa6906e8028748938f9159807fd039af4
   YYImage: 1e1b62a9997399593e4b9c4ecfbbabbf1d3f3b54
 
-PODFILE CHECKSUM: 820287bc7925d7c20e02a02923976c60b1f5386b
+PODFILE CHECKSUM: b4815f8e6306c08266b24710736a8c956b666aa1
 
 COCOAPODS: 1.5.3
diff --git a/SignalServiceKit/src/Messages/OWSMessageDecrypter.m b/SignalServiceKit/src/Messages/OWSMessageDecrypter.m
index 44b14d46a..35817bcba 100644
--- a/SignalServiceKit/src/Messages/OWSMessageDecrypter.m
+++ b/SignalServiceKit/src/Messages/OWSMessageDecrypter.m
@@ -138,6 +138,11 @@ NSError *EnsureDecryptError(NSError *_Nullable error, NSString *fallbackErrorDes
     return [self.blockingManager.blockedPhoneNumbers containsObject:envelope.source];
 }
 
+- (TSAccountManager *)tsAccountManager
+{
+    return TSAccountManager.sharedInstance;
+}
+
 #pragma mark - Decryption
 
 - (void)decryptEnvelope:(SSKProtoEnvelope *)envelope
@@ -161,6 +166,8 @@ NSError *EnsureDecryptError(NSError *_Nullable error, NSString *fallbackErrorDes
         });
     };
 
+    NSString *localRecipientId = self.tsAccountManager.localNumber;
+    uint32_t localDeviceId = OWSDevicePrimaryDeviceId;
     DecryptSuccessBlock successBlock = ^(
         OWSMessageDecryptResult *result, YapDatabaseReadWriteTransaction *transaction) {
         // Ensure all blocked messages are discarded.
@@ -169,11 +176,9 @@ NSError *EnsureDecryptError(NSError *_Nullable error, NSString *fallbackErrorDes
             return failureBlock();
         }
 
-        if ([result.source isEqualToString:TSAccountManager.sharedInstance.localNumber]
-            && result.sourceDevice == OWSDevicePrimaryDeviceId) {
-            OWSAssertDebug(result.isUDMessage);
-
-            OWSLogInfo(@"Ignoring self-sent sync message.");
+        if ([result.source isEqualToString:localRecipientId] && result.sourceDevice == localDeviceId) {
+            // Self-sent messages should be discarded during the decryption process.
+            OWSFailDebug(@"Unexpected self-sent sync message.");
             return failureBlock();
         }
 
@@ -427,6 +432,9 @@ NSError *EnsureDecryptError(NSError *_Nullable error, NSString *fallbackErrorDes
     id<SMKCertificateValidator> certificateValidator =
         [[SMKCertificateDefaultValidator alloc] initWithTrustRoot:self.udManager.trustRoot];
 
+    NSString *localRecipientId = self.tsAccountManager.localNumber;
+    uint32_t localDeviceId = OWSDevicePrimaryDeviceId;
+
     [self.dbConnection asyncReadWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {
         @try {
             NSError *error;
@@ -446,9 +454,16 @@ NSError *EnsureDecryptError(NSError *_Nullable error, NSString *fallbackErrorDes
                 [cipher decryptMessageWithCertificateValidator:certificateValidator
                                                 cipherTextData:encryptedData
                                                      timestamp:serverTimestamp
+                                              localRecipientId:localRecipientId
+                                                 localDeviceId:localDeviceId
                                                protocolContext:transaction
                                                          error:&error];
             if (error || !decryptResult) {
+                if ([error.domain isEqualToString:@"SignalMetadataKit.SMKSelfSentMessageError"]) {
+                    // Self-sent messages can be safely discarded.
+                    return failureBlock(error);
+                }
+
                 OWSFailDebug(@"Could not decrypt UD message: %@", error);
                 error = EnsureDecryptError(error, @"Could not decrypt UD message");
                 return failureBlock(error);
@@ -531,7 +546,12 @@ NSError *EnsureDecryptError(NSError *_Nullable error, NSString *fallbackErrorDes
             return;
         } else {
             OWSProdErrorWEnvelope([OWSAnalyticsEvents messageManagerErrorCorruptMessage], envelope);
-            errorMessage = [TSErrorMessage corruptedMessageWithEnvelope:envelope withTransaction:transaction];
+            if (envelope.source.length > 0) {
+                errorMessage = [TSErrorMessage corruptedMessageWithEnvelope:envelope withTransaction:transaction];
+            } else {
+                // TODO: Find another way to surface undecryptable UD messages to the user.
+                return;
+            }
         }
 
         OWSAssertDebug(errorMessage);
diff --git a/SignalServiceKit/src/Messages/OWSMessageSender.m b/SignalServiceKit/src/Messages/OWSMessageSender.m
index cf2d6d1cd..d091dc94d 100644
--- a/SignalServiceKit/src/Messages/OWSMessageSender.m
+++ b/SignalServiceKit/src/Messages/OWSMessageSender.m
@@ -1331,7 +1331,6 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
     OWSAssertDebug(deviceIds);
 
     if (messageSend.isUDSend && messageSend.isLocalNumber) {
-        const NSUInteger kLocalDeviceId = 1;
         OWSAssertDebug(![deviceIds containsObject:@(OWSDevicePrimaryDeviceId)]);
 
         [deviceIds addObject:@(OWSDevicePrimaryDeviceId)];