diff --git a/libsignal/service/src/test/java/org/whispersystems/signalservice/api/crypto/AttachmentCipherTest.java b/libsignal/service/src/test/java/org/whispersystems/signalservice/api/crypto/AttachmentCipherTest.java
index 8c273ed760..96f922372f 100644
--- a/libsignal/service/src/test/java/org/whispersystems/signalservice/api/crypto/AttachmentCipherTest.java
+++ b/libsignal/service/src/test/java/org/whispersystems/signalservice/api/crypto/AttachmentCipherTest.java
@@ -129,7 +129,7 @@ public class AttachmentCipherTest extends TestCase {
       EncryptResult encryptResult    = encryptData(plaintextInput, key);
       byte[]        badMacCiphertext = Arrays.copyOf(encryptResult.ciphertext, encryptResult.ciphertext.length);
 
-      badMacCiphertext[badMacCiphertext.length - 1] = 0;
+      badMacCiphertext[badMacCiphertext.length - 1] += 1;
 
       cipherFile = writeToFile(badMacCiphertext);
 
@@ -191,7 +191,7 @@ public class AttachmentCipherTest extends TestCase {
       EncryptResult encryptResult    = encryptData(plaintextInput, expandPackKey(packKey));
       byte[]        badMacCiphertext = Arrays.copyOf(encryptResult.ciphertext, encryptResult.ciphertext.length);
 
-      badMacCiphertext[badMacCiphertext.length - 1] = 0;
+      badMacCiphertext[badMacCiphertext.length - 1] += 1;
 
       AttachmentCipherInputStream.createForStickerData(badMacCiphertext, packKey);
     } catch (InvalidMessageException e) {