diff --git a/data/src/main/java/org/cryptomator/data/cloud/crypto/MasterkeyCryptoCloudProvider.java b/data/src/main/java/org/cryptomator/data/cloud/crypto/MasterkeyCryptoCloudProvider.java
index 2ea3cc6d..60806d53 100644
--- a/data/src/main/java/org/cryptomator/data/cloud/crypto/MasterkeyCryptoCloudProvider.java
+++ b/data/src/main/java/org/cryptomator/data/cloud/crypto/MasterkeyCryptoCloudProvider.java
@@ -12,6 +12,7 @@ import org.cryptomator.domain.Vault;
 import org.cryptomator.domain.exception.BackendException;
 import org.cryptomator.domain.exception.CancellationException;
 import org.cryptomator.domain.exception.FatalBackendException;
+import org.cryptomator.domain.exception.vaultconfig.UnsupportedMasterkeyLocationException;
 import org.cryptomator.domain.repository.CloudContentRepository;
 import org.cryptomator.domain.usecases.cloud.ByteArrayDataSource;
 import org.cryptomator.domain.usecases.cloud.Flag;
@@ -161,8 +162,9 @@ public class MasterkeyCryptoCloudProvider implements CryptoCloudProvider {
 
 	private CloudFile masterkeyFile(CloudFolder vaultLocation, UnverifiedVaultConfig unverifiedVaultConfig) throws BackendException {
 		String path = unverifiedVaultConfig.getKeyId().getSchemeSpecificPart();
-		// TODO / FIXME sanitize path and throw specific exception
-		//throw new UnsupportedMasterkeyLocationException(unverifiedVaultConfig);
+		if(!path.equals(MASTERKEY_FILE_NAME)) {
+			throw new UnsupportedMasterkeyLocationException(unverifiedVaultConfig);
+		}
 		return cloudContentRepository.file(vaultLocation, path);
 	}
 
diff --git a/presentation/src/main/java/org/cryptomator/presentation/exception/ExceptionHandlers.kt b/presentation/src/main/java/org/cryptomator/presentation/exception/ExceptionHandlers.kt
index e4769223..adb07a36 100644
--- a/presentation/src/main/java/org/cryptomator/presentation/exception/ExceptionHandlers.kt
+++ b/presentation/src/main/java/org/cryptomator/presentation/exception/ExceptionHandlers.kt
@@ -18,6 +18,7 @@ import org.cryptomator.domain.exception.license.NoLicenseAvailableException
 import org.cryptomator.domain.exception.update.GeneralUpdateErrorException
 import org.cryptomator.domain.exception.update.HashMismatchUpdateCheckException
 import org.cryptomator.domain.exception.update.SSLHandshakePreAndroid5UpdateCheckException
+import org.cryptomator.domain.exception.vaultconfig.UnsupportedMasterkeyLocationException
 import org.cryptomator.domain.exception.vaultconfig.VaultConfigLoadException
 import org.cryptomator.domain.exception.vaultconfig.VaultKeyInvalidException
 import org.cryptomator.domain.exception.vaultconfig.VaultVersionMismatchException
@@ -54,6 +55,7 @@ class ExceptionHandlers @Inject constructor(private val context: Context, defaul
 		staticHandler(VaultVersionMismatchException::class.java, R.string.error_vault_version_mismatch)
 		staticHandler(VaultKeyInvalidException::class.java, R.string.error_vault_key_invalid)
 		staticHandler(VaultConfigLoadException::class.java, R.string.error_vault_config_loading)
+		staticHandler(UnsupportedMasterkeyLocationException::class.java, R.string.error_masterkey_location_not_supported)
 		staticHandler(NoSuchBucketException::class.java, R.string.error_no_such_bucket)
 		exceptionHandlers.add(MissingCryptorExceptionHandler())
 		exceptionHandlers.add(CancellationExceptionHandler())
diff --git a/presentation/src/main/java/org/cryptomator/presentation/presenter/UnlockVaultPresenter.kt b/presentation/src/main/java/org/cryptomator/presentation/presenter/UnlockVaultPresenter.kt
index c9375dba..586e6347 100644
--- a/presentation/src/main/java/org/cryptomator/presentation/presenter/UnlockVaultPresenter.kt
+++ b/presentation/src/main/java/org/cryptomator/presentation/presenter/UnlockVaultPresenter.kt
@@ -107,8 +107,8 @@ class UnlockVaultPresenter @Inject constructor(
 			}
 			view?.showBiometricDialog(vaultModel)
 		} else {
-			startPrepareUnlockUseCase(vaultModel.toVault())
 			view?.showEnterPasswordDialog(vaultModel)
+			startPrepareUnlockUseCase(vaultModel.toVault())
 		}
 	}
 
diff --git a/presentation/src/main/res/values/strings.xml b/presentation/src/main/res/values/strings.xml
index 73341cfb..dae556a2 100644
--- a/presentation/src/main/res/values/strings.xml
+++ b/presentation/src/main/res/values/strings.xml
@@ -38,6 +38,7 @@
 	<string name="error_vault_config_loading">General error while loading the vault config</string>
 	<string name="error_file_not_found_after_opening_using_3party">Local file isn\'t present anymore after switching back to Cryptomator. Possible changes cannot be propagated back to the cloud.</string>
 	<string name="error_no_such_bucket">No such bucket</string>
+	<string name="error_masterkey_location_not_supported">Custom Masterkey location not supported yet</string>
 
 	<!-- # clouds -->