diff --git a/main/commons/src/main/java/org/cryptomator/common/vaults/LockNotCompletedException.java b/main/commons/src/main/java/org/cryptomator/common/vaults/LockNotCompletedException.java
new file mode 100644
index 000000000..237630da0
--- /dev/null
+++ b/main/commons/src/main/java/org/cryptomator/common/vaults/LockNotCompletedException.java
@@ -0,0 +1,12 @@
+package org.cryptomator.common.vaults;
+
+public class LockNotCompletedException extends Exception {
+
+	public LockNotCompletedException(String reason) {
+		super(reason);
+	}
+
+	public LockNotCompletedException(Throwable cause) {
+		super(cause);
+	}
+}
diff --git a/main/commons/src/main/java/org/cryptomator/common/vaults/Vault.java b/main/commons/src/main/java/org/cryptomator/common/vaults/Vault.java
index f10eb3968..fae92b3b7 100644
--- a/main/commons/src/main/java/org/cryptomator/common/vaults/Vault.java
+++ b/main/commons/src/main/java/org/cryptomator/common/vaults/Vault.java
@@ -140,14 +140,7 @@ public class Vault {
 			cryptoFileSystem.set(fs);
 			try {
 				volume = volumeProvider.get();
-				volume.mount(fs, getEffectiveMountFlags(), throwable -> {
-					LOG.info("Unmounted vault '{}'", getDisplayName());
-					destroyCryptoFileSystem();
-					state.set(VaultState.Value.LOCKED);
-					if (throwable != null) {
-						LOG.warn("Unexpected unmount and lock of vault " + getDisplayName(), throwable);
-					}
-				});
+				volume.mount(fs, getEffectiveMountFlags(), this::lockOnVolumeExit);
 			} catch (Exception e) {
 				destroyCryptoFileSystem();
 				throw e;
@@ -157,21 +150,32 @@ public class Vault {
 		}
 	}
 
-	public synchronized void lock(boolean forced) throws VolumeException {
+	private void lockOnVolumeExit(Throwable t) {
+		LOG.info("Unmounted vault '{}'", getDisplayName());
+		destroyCryptoFileSystem();
+		state.set(VaultState.Value.LOCKED);
+		if (t != null) {
+			LOG.warn("Unexpected unmount and lock of vault " + getDisplayName(), t);
+		}
+	}
+
+	public synchronized void lock(boolean forced) throws VolumeException, LockNotCompletedException {
+		//initiate unmount
 		if (forced && volume.supportsForcedUnmount()) {
 			volume.unmountForced();
 		} else {
 			volume.unmount();
 		}
-		destroyCryptoFileSystem();
+
+		//wait for lockOnVolumeExit to be executed
 		try {
 			boolean locked = state.awaitState(VaultState.Value.LOCKED, 3000, TimeUnit.MILLISECONDS);
 			if (!locked) {
-				throw new VolumeException("Locking failed"); //FIXME: other exception
+				throw new LockNotCompletedException("Locking of vault " + this.getDisplayName() + " still in progress.");
 			}
 		} catch (InterruptedException e) {
 			Thread.currentThread().interrupt();
-			throw new VolumeException("Lock failed."); //FIXME: other/new exception
+			throw new LockNotCompletedException(e);
 		}
 	}
 
diff --git a/main/ui/src/main/java/org/cryptomator/ui/common/VaultService.java b/main/ui/src/main/java/org/cryptomator/ui/common/VaultService.java
index 6555904e5..b81ddec49 100644
--- a/main/ui/src/main/java/org/cryptomator/ui/common/VaultService.java
+++ b/main/ui/src/main/java/org/cryptomator/ui/common/VaultService.java
@@ -1,5 +1,6 @@
 package org.cryptomator.ui.common;
 
+import org.cryptomator.common.vaults.LockNotCompletedException;
 import org.cryptomator.common.vaults.Vault;
 import org.cryptomator.common.vaults.VaultState;
 import org.cryptomator.common.vaults.Volume;
@@ -175,7 +176,7 @@ public class VaultService {
 		}
 
 		@Override
-		protected Vault call() throws Volume.VolumeException {
+		protected Vault call() throws Volume.VolumeException, LockNotCompletedException {
 			vault.lock(forced);
 			return vault;
 		}
diff --git a/main/ui/src/main/java/org/cryptomator/ui/launcher/AppLifecycleListener.java b/main/ui/src/main/java/org/cryptomator/ui/launcher/AppLifecycleListener.java
index 5e2ed383a..75af409f1 100644
--- a/main/ui/src/main/java/org/cryptomator/ui/launcher/AppLifecycleListener.java
+++ b/main/ui/src/main/java/org/cryptomator/ui/launcher/AppLifecycleListener.java
@@ -1,6 +1,7 @@
 package org.cryptomator.ui.launcher;
 
 import org.cryptomator.common.ShutdownHook;
+import org.cryptomator.common.vaults.LockNotCompletedException;
 import org.cryptomator.common.vaults.Vault;
 import org.cryptomator.common.vaults.VaultState;
 import org.cryptomator.common.vaults.Volume;
@@ -129,6 +130,8 @@ public class AppLifecycleListener {
 					vault.lock(true);
 				} catch (Volume.VolumeException e) {
 					LOG.error("Failed to unmount vault " + vault.getPath(), e);
+				} catch (LockNotCompletedException e) {
+					LOG.error("Failed to lock vault " + vault.getPath(), e);
 				}
 			}
 		}
diff --git a/main/ui/src/main/java/org/cryptomator/ui/lock/LockWorkflow.java b/main/ui/src/main/java/org/cryptomator/ui/lock/LockWorkflow.java
index 5566caeb0..87fd486f2 100644
--- a/main/ui/src/main/java/org/cryptomator/ui/lock/LockWorkflow.java
+++ b/main/ui/src/main/java/org/cryptomator/ui/lock/LockWorkflow.java
@@ -1,6 +1,7 @@
 package org.cryptomator.ui.lock;
 
 import dagger.Lazy;
+import org.cryptomator.common.vaults.LockNotCompletedException;
 import org.cryptomator.common.vaults.Vault;
 import org.cryptomator.common.vaults.VaultState;
 import org.cryptomator.common.vaults.Volume;
@@ -49,10 +50,10 @@ public class LockWorkflow extends Task<Void> {
 	}
 
 	@Override
-	protected Void call() throws Volume.VolumeException, InterruptedException {
+	protected Void call() throws Volume.VolumeException, InterruptedException, LockNotCompletedException {
 		try {
 			vault.lock(false);
-		} catch (Volume.VolumeException e) {
+		} catch (Volume.VolumeException | LockNotCompletedException e) {
 			LOG.debug("Regular lock of {} failed.", vault.getDisplayName(), e);
 			var decision = askUserForAction();
 			switch (decision) {