diff --git a/apps/client/eslint.config.cjs b/apps/client/eslint.config.cjs
index 96ecefd50..bcbe2c1c1 100644
--- a/apps/client/eslint.config.cjs
+++ b/apps/client/eslint.config.cjs
@@ -47,7 +47,9 @@ module.exports = [
   {
     files: ['**/*.ts', '**/*.tsx'],
     // Override or add rules here
-    rules: {}
+    rules: {
+      '@typescript-eslint/prefer-nullish-coalescing': 'error'
+    }
   },
   {
     files: ['**/*.js', '**/*.jsx'],
diff --git a/apps/client/jest.config.ts b/apps/client/jest.config.ts
index 04378bdbd..72e011ae9 100644
--- a/apps/client/jest.config.ts
+++ b/apps/client/jest.config.ts
@@ -1,4 +1,4 @@
-/* eslint-disable */
+ 
 export default {
   displayName: 'client',
 
diff --git a/apps/client/src/app/components/admin-market-data/asset-profile-dialog/asset-profile-dialog.component.ts b/apps/client/src/app/components/admin-market-data/asset-profile-dialog/asset-profile-dialog.component.ts
index 967a289ef..c34e8eb78 100644
--- a/apps/client/src/app/components/admin-market-data/asset-profile-dialog/asset-profile-dialog.component.ts
+++ b/apps/client/src/app/components/admin-market-data/asset-profile-dialog/asset-profile-dialog.component.ts
@@ -550,7 +550,7 @@ export class GfAssetProfileDialogComponent implements OnInit {
         ) as Record<string, string>,
         locale:
           this.assetProfileForm.controls.scraperConfiguration.controls.locale
-            ?.value || undefined,
+            ?.value ?? undefined,
         mode:
           this.assetProfileForm.controls.scraperConfiguration.controls.mode
             ?.value ?? undefined,
@@ -599,7 +599,7 @@ export class GfAssetProfileDialogComponent implements OnInit {
       assetClass: this.assetProfileForm.controls.assetClass.value ?? undefined,
       assetSubClass:
         this.assetProfileForm.controls.assetSubClass.value ?? undefined,
-      comment: this.assetProfileForm.controls.comment.value || undefined,
+      comment: this.assetProfileForm.controls.comment.value ?? undefined,
       currency: this.assetProfileForm.controls.currency.value ?? undefined,
       dataGatheringFrequency:
         this.assetProfileForm.controls.dataGatheringFrequency.value ??
@@ -607,8 +607,8 @@ export class GfAssetProfileDialogComponent implements OnInit {
       isActive: isBoolean(this.assetProfileForm.controls.isActive.value)
         ? this.assetProfileForm.controls.isActive.value
         : undefined,
-      name: this.assetProfileForm.controls.name.value || undefined,
-      url: this.assetProfileForm.controls.url.value || undefined
+      name: this.assetProfileForm.controls.name.value ?? undefined,
+      url: this.assetProfileForm.controls.url.value ?? undefined
     };
 
     try {
@@ -743,7 +743,7 @@ export class GfAssetProfileDialogComponent implements OnInit {
           ) as Record<string, string>,
           locale:
             this.assetProfileForm.controls.scraperConfiguration.controls.locale
-              ?.value || undefined,
+              ?.value ?? undefined,
           mode: this.assetProfileForm.controls.scraperConfiguration.controls
             .mode?.value,
           selector:
diff --git a/apps/client/src/app/components/home-holdings/home-holdings.component.ts b/apps/client/src/app/components/home-holdings/home-holdings.component.ts
index cf7e52833..bf70bf8e0 100644
--- a/apps/client/src/app/components/home-holdings/home-holdings.component.ts
+++ b/apps/client/src/app/components/home-holdings/home-holdings.component.ts
@@ -181,8 +181,8 @@ export class GfHomeHoldingsComponent implements OnInit {
       this.viewModeFormControl.setValue(
         this.deviceType === 'mobile'
           ? GfHomeHoldingsComponent.DEFAULT_HOLDINGS_VIEW_MODE
-          : this.user?.settings?.holdingsViewMode ||
-              GfHomeHoldingsComponent.DEFAULT_HOLDINGS_VIEW_MODE,
+          : (this.user?.settings?.holdingsViewMode ??
+              GfHomeHoldingsComponent.DEFAULT_HOLDINGS_VIEW_MODE),
         { emitEvent: false }
       );
     } else if (this.holdingType === 'CLOSED') {
diff --git a/apps/client/src/app/pages/accounts/create-or-update-account-dialog/create-or-update-account-dialog.component.ts b/apps/client/src/app/pages/accounts/create-or-update-account-dialog/create-or-update-account-dialog.component.ts
index ca88120ca..d27b5ceae 100644
--- a/apps/client/src/app/pages/accounts/create-or-update-account-dialog/create-or-update-account-dialog.component.ts
+++ b/apps/client/src/app/pages/accounts/create-or-update-account-dialog/create-or-update-account-dialog.component.ts
@@ -200,12 +200,12 @@ export class GfCreateOrUpdateAccountDialogComponent {
   protected async onSubmit() {
     const account: CreateAccountDto | UpdateAccountDto = {
       balance: this.accountForm.get('balance')?.value,
-      comment: this.accountForm.get('comment')?.value || null,
+      comment: this.accountForm.get('comment')?.value ?? null,
       currency: this.accountForm.get('currency')?.value,
       id: this.accountForm.get('accountId')?.value,
       isExcluded: this.accountForm.get('isExcluded')?.value,
       name: this.accountForm.get('name')?.value,
-      platformId: this.accountForm.get('platformId')?.value?.id || null,
+      platformId: this.accountForm.get('platformId')?.value?.id ?? null,
       tags: this.accountForm
         .get('tags')
         ?.value?.filter(({ id }: Tag) => {
diff --git a/apps/client/src/app/pages/portfolio/activities/create-or-update-activity-dialog/create-or-update-activity-dialog.component.ts b/apps/client/src/app/pages/portfolio/activities/create-or-update-activity-dialog/create-or-update-activity-dialog.component.ts
index 022a8f2a2..769638022 100644
--- a/apps/client/src/app/pages/portfolio/activities/create-or-update-activity-dialog/create-or-update-activity-dialog.component.ts
+++ b/apps/client/src/app/pages/portfolio/activities/create-or-update-activity-dialog/create-or-update-activity-dialog.component.ts
@@ -493,7 +493,7 @@ export class GfCreateOrUpdateActivityDialogComponent {
       accountId: this.activityForm.get('accountId')?.value,
       assetClass: this.activityForm.get('assetClass')?.value,
       assetSubClass: this.activityForm.get('assetSubClass')?.value,
-      comment: this.activityForm.get('comment')?.value || null,
+      comment: this.activityForm.get('comment')?.value ?? null,
       currency: this.activityForm.get('currency')?.value,
       customCurrency: this.activityForm.get('currencyOfUnitPrice')?.value,
       dataSource: ['FEE', 'INTEREST', 'LIABILITY', 'VALUABLE'].includes(
diff --git a/apps/client/src/app/services/user/user.service.ts b/apps/client/src/app/services/user/user.service.ts
index 52f33dc5a..d58f77c3e 100644
--- a/apps/client/src/app/services/user/user.service.ts
+++ b/apps/client/src/app/services/user/user.service.ts
@@ -192,6 +192,6 @@ export class UserService extends ObservableStore<UserStoreState> {
       return throwError(errMessage);
     }
 
-    return throwError(error || 'Server error');
+    return throwError(error ?? 'Server error');
   }
 }