diff --git a/app/src/main/java/cash/z/ecc/android/ui/setup/BackupFragment.kt b/app/src/main/java/cash/z/ecc/android/ui/setup/BackupFragment.kt
index 64aef46..5bf9cd2 100644
--- a/app/src/main/java/cash/z/ecc/android/ui/setup/BackupFragment.kt
+++ b/app/src/main/java/cash/z/ecc/android/ui/setup/BackupFragment.kt
@@ -89,12 +89,18 @@ class BackupFragment : BaseFragment<FragmentBackupBinding>() {
         }
     }
 
+    // TODO: move this into the SDK
     private suspend fun calculateBirthday(): Int {
         var storedBirthday: Int = 0
         var oldestTransactionHeight:Int = 0
         try {
-            storedBirthday = walletSetup.loadBirthdayHeight()
+            storedBirthday = walletSetup.loadBirthdayHeight() ?: 0
             oldestTransactionHeight = mainActivity?.synchronizerComponent?.synchronizer()?.receivedTransactions?.first()?.last()?.minedHeight ?: 0
+            // to be safe adjust for reorgs (and generally a little cushion is good for privacy)
+            // so we round down to the nearest 100 and then subtract 100 to ensure that the result is always at least 100 blocks away
+            oldestTransactionHeight = ZcashSdk.MAX_REORG_SIZE.let { boundary ->
+                oldestTransactionHeight.let { it - it.rem(boundary) - boundary }
+            }
         } catch (t: Throwable) {
             twig("failed to calculate birthday due to: $t")
         }