diff --git a/src/lib/services/constants.ts b/src/lib/services/constants.ts
index 35fb16f..65eb969 100644
--- a/src/lib/services/constants.ts
+++ b/src/lib/services/constants.ts
@@ -1 +1,2 @@
 export const CONFLICT_ERROR_CODE = 409;
+export const CHANGED_CHECK_INTERVAL = 3000;
diff --git a/src/lib/services/generic.service.ts b/src/lib/services/generic.service.ts
index 5d12fb0..ce346b4 100644
--- a/src/lib/services/generic.service.ts
+++ b/src/lib/services/generic.service.ts
@@ -26,9 +26,8 @@ export abstract class GenericService<I> {
     protected constructor(protected readonly _injector: Injector, protected readonly _defaultModelPath: string) {}
 
     protected get _hasChanges$(): Observable<boolean> {
-        return this._post<{ value: boolean }>({ since: this._lastCheckedForChanges }, `${this._defaultModelPath}/changes`).pipe(
-            map(res => res.value),
-            tap(() => this._updateLastChanged()),
+        return this._post<{ value: boolean }>({ value: this._lastCheckedForChanges }, `${this._defaultModelPath}/changes`).pipe(
+            map((res: { value: boolean }) => res.value),
         );
     }