diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/storage/AccountsManager.java b/service/src/main/java/org/whispersystems/textsecuregcm/storage/AccountsManager.java
index 9208d9a82..644d0b4c7 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/storage/AccountsManager.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/storage/AccountsManager.java
@@ -292,6 +292,7 @@ public class AccountsManager {
 
       final UUID uuid = account.getUuid();
       final String originalNumber = account.getNumber();
+      final UUID originalPhoneNumberIdentifier = account.getPhoneNumberIdentifier();
 
       updatedAccount = updateWithRetries(account,
           updater,
@@ -305,6 +306,13 @@ public class AccountsManager {
             new RuntimeException());
       }
 
+      assert updatedAccount.getPhoneNumberIdentifier().equals(originalPhoneNumberIdentifier);
+
+      if (!updatedAccount.getPhoneNumberIdentifier().equals(originalPhoneNumberIdentifier)) {
+        logger.error("Phone number identifier changed via \"normal\" update; PNIs must be changed via changeNumber method",
+            new RuntimeException());
+      }
+
       redisSet(updatedAccount);
     }
 
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/AccountsManagerTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/AccountsManagerTest.java
index c37c3971e..5df767be7 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/AccountsManagerTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/AccountsManagerTest.java
@@ -355,18 +355,19 @@ class AccountsManagerTest {
   @Test
   void testUpdate_optimisticLockingFailure() {
     UUID uuid = UUID.randomUUID();
-    Account account = new Account("+14152222222", uuid, UUID.randomUUID(), new HashSet<>(), new byte[16]);
+    UUID pni = UUID.randomUUID();
+    Account account = new Account("+14152222222", uuid, pni, new HashSet<>(), new byte[16]);
 
     when(commands.get(eq("Account3::" + uuid))).thenReturn(null);
 
     when(accounts.getByAccountIdentifier(uuid)).thenReturn(
-        Optional.of(new Account("+14152222222", uuid, UUID.randomUUID(), new HashSet<>(), new byte[16])));
+        Optional.of(new Account("+14152222222", uuid, pni, new HashSet<>(), new byte[16])));
     doThrow(ContestedOptimisticLockException.class)
         .doAnswer(ACCOUNT_UPDATE_ANSWER)
         .when(accounts).update(any());
 
     when(accounts.getByAccountIdentifier(uuid)).thenReturn(
-        Optional.of(new Account("+14152222222", uuid, UUID.randomUUID(), new HashSet<>(), new byte[16])));
+        Optional.of(new Account("+14152222222", uuid, pni, new HashSet<>(), new byte[16])));
     doThrow(ContestedOptimisticLockException.class)
         .doAnswer(ACCOUNT_UPDATE_ANSWER)
         .when(accounts).update(any());