diff --git a/web/database/utils/WorkerConnectionProxy.js b/web/database/utils/WorkerConnectionProxy.js
--- a/web/database/utils/WorkerConnectionProxy.js
+++ b/web/database/utils/WorkerConnectionProxy.js
@@ -35,7 +35,7 @@
 
     if (!id || !this.promiseCallbacks[id]) {
       if (error) {
-        this.onError(error);
+        this.onError(new Error(error));
       } else if (message) {
         this.onError(new Error(`Unknown error for message: ${message.type}`));
       } else {
@@ -46,7 +46,7 @@
 
     const callbacks = this.promiseCallbacks[id];
     if (error) {
-      callbacks.reject(error);
+      callbacks.reject(new Error(error));
     } else {
       callbacks.resolve(message);
     }
diff --git a/web/database/worker/db-worker.js b/web/database/worker/db-worker.js
--- a/web/database/worker/db-worker.js
+++ b/web/database/worker/db-worker.js
@@ -286,7 +286,7 @@
 
     if (!id) {
       port.postMessage({
-        error: new Error('Request without identifier'),
+        error: 'Request without identifier',
       });
     }
 
@@ -299,7 +299,7 @@
     } catch (e) {
       port.postMessage({
         id,
-        error: e,
+        error: e.message,
       });
     }
   };
diff --git a/web/types/worker-types.js b/web/types/worker-types.js
--- a/web/types/worker-types.js
+++ b/web/types/worker-types.js
@@ -135,7 +135,7 @@
 export type WorkerResponseProxyMessage = {
   +id?: number,
   +message?: WorkerResponseMessage,
-  +error?: Error,
+  +error?: string,
 };
 
 // SharedWorker types