diff --git a/frontend/sync-client/src/persistence/database.ts b/frontend/sync-client/src/persistence/database.ts
index 0987c0de..2bcd77bc 100644
--- a/frontend/sync-client/src/persistence/database.ts
+++ b/frontend/sync-client/src/persistence/database.ts
@@ -301,6 +301,11 @@ export class Database {
 		);
 
 		let newDocument = this.getLatestDocumentByRelativePath(newRelativePath);
+		if (newDocument !== undefined && !newDocument.isDeleted) {
+			throw new Error(
+				`Document already exists at new location: ${newRelativePath}`
+			);
+		}
 
 		// It's either an invalid state of newDocument is pending deletion and we have
 		// to wait for it to complete.
diff --git a/frontend/sync-client/src/services/connected-state.ts b/frontend/sync-client/src/services/connected-state.ts
index da522816..e21ad005 100644
--- a/frontend/sync-client/src/services/connected-state.ts
+++ b/frontend/sync-client/src/services/connected-state.ts
@@ -1,4 +1,3 @@
-import { Syncer } from "../sync-operations/syncer";
 import { Settings } from "../persistence/settings";
 import { Logger } from "../tracing/logger";
 import { createPromise } from "../utils/create-promise";
diff --git a/frontend/sync-client/src/utils/hash.ts b/frontend/sync-client/src/utils/hash.ts
index 10f20d1d..cd965db5 100644
--- a/frontend/sync-client/src/utils/hash.ts
+++ b/frontend/sync-client/src/utils/hash.ts
@@ -6,7 +6,7 @@ export function hash(content: Uint8Array): string {
 		result = (result << 5) - result + content[i];
 		result |= 0; // Convert to 32bit integer
 	}
-	return Math.abs(result).toString(16);
+	return Math.abs(result).toString(16).padStart(8, "0");
 }
 
 export const EMPTY_HASH = hash(new Uint8Array(0));
diff --git a/frontend/test-client/src/cli.ts b/frontend/test-client/src/cli.ts
index e1a6fd5b..8e6e711b 100644
--- a/frontend/test-client/src/cli.ts
+++ b/frontend/test-client/src/cli.ts
@@ -92,7 +92,7 @@ async function runTest({
 async function runTests(): Promise<void> {
 	const agentCounts = [2, 8];
 	const jitterScaleInSeconds = [0.5, 0, 2];
-	const concurrencies = [16, 1];
+	const concurrencies = [1];
 	const iterations = [50, 200];
 	const doDeletes = [true, false];