diff --git a/src/cryfs/filesystem/CryDevice.cpp b/src/cryfs/filesystem/CryDevice.cpp
index 3d1f6dd8..bed53960 100644
--- a/src/cryfs/filesystem/CryDevice.cpp
+++ b/src/cryfs/filesystem/CryDevice.cpp
@@ -104,7 +104,7 @@ unique_ref<BlockStore2> CryDevice::CreateIntegrityEncryptedBlockStore(unique_ref
 #ifndef CRYFS_NO_COMPATIBILITY
   if (!configFile->config()->HasVersionNumbers()) {
     IntegrityBlockStore2::migrateFromBlockstoreWithoutVersionNumbers(encryptedBlockStore.get(), integrityFilePath, myClientId);
-    configFile->config()->SetBlocksizeBytes(configFile->config()->BlocksizeBytes() + IntegrityBlockStore2::HEADER_LENGTH);
+    configFile->config()->SetBlocksizeBytes(configFile->config()->BlocksizeBytes() + IntegrityBlockStore2::HEADER_LENGTH - blockstore::BlockId::BINARY_LENGTH); // Minus BlockId size because EncryptedBlockStore doesn't store the BlockId anymore (that was moved to IntegrityBlockStore)
     configFile->config()->SetHasVersionNumbers(true);
     configFile->save();
   }