diff --git a/lib/ui/app/entity_dropdown.dart b/lib/ui/app/entity_dropdown.dart
index ade804b11..e27dd7f84 100644
--- a/lib/ui/app/entity_dropdown.dart
+++ b/lib/ui/app/entity_dropdown.dart
@@ -51,7 +51,7 @@ class EntityDropdown extends StatefulWidget {
   final bool? autofocus;
   final BuiltMap<String?, SelectableEntity?>? entityMap;
   final Function(SelectableEntity?) onSelected;
-  final Function? validator;
+  final String? Function(String?)? validator;
   final bool autoValidate;
   final bool allowClearing;
   final Function(String?)? onFieldSubmitted;
@@ -331,7 +331,7 @@ class _EntityDropdownState extends State<EntityDropdown> {
             FocusNode focusNode,
             VoidCallback onFieldSubmitted) {
           return DecoratedFormField(
-            validator: widget.validator as dynamic Function(String)?,
+            validator: widget.validator,
             showClear: showClear,
             label: widget.labelText,
             autofocus:
@@ -424,7 +424,7 @@ class _EntityDropdownState extends State<EntityDropdown> {
             child: TextFormField(
               focusNode: _focusNode,
               readOnly: true,
-              validator: widget.validator as String? Function(String?)?,
+              validator: widget.validator,
               autovalidateMode: widget.autoValidate
                   ? AutovalidateMode.always
                   : AutovalidateMode.onUserInteraction,
diff --git a/lib/ui/app/forms/client_picker.dart b/lib/ui/app/forms/client_picker.dart
index 17ddb46ef..78de6ff07 100644
--- a/lib/ui/app/forms/client_picker.dart
+++ b/lib/ui/app/forms/client_picker.dart
@@ -49,7 +49,7 @@ class ClientPicker extends StatelessWidget {
       entityList: memoizedDropdownClientList(clientState.map, clientState.list,
           state.userState.map, state.staticState),
       entityMap: clientState.map,
-      validator: (String val) => isRequired && val.trim().isEmpty
+      validator: (String? val) => isRequired && (val ?? '').trim().isEmpty
           ? AppLocalization.of(context)!.pleaseSelectAClient
           : null,
       onSelected: onSelected,
diff --git a/lib/ui/app/forms/vendor_picker.dart b/lib/ui/app/forms/vendor_picker.dart
index e31d2436c..31696e2d1 100644
--- a/lib/ui/app/forms/vendor_picker.dart
+++ b/lib/ui/app/forms/vendor_picker.dart
@@ -46,7 +46,7 @@ class VendorPicker extends StatelessWidget {
       entityList: memoizedDropdownVendorList(vendorState.map, vendorState.list,
           state.userState.map, state.staticState),
       entityMap: vendorState.map,
-      validator: (String val) => val.trim().isEmpty
+      validator: (String? val) => (val ?? '').trim().isEmpty
           ? AppLocalization.of(context)!.pleaseSelectAVendor
           : null,
       onSelected: onSelected,
diff --git a/lib/ui/payment/edit/payment_edit.dart b/lib/ui/payment/edit/payment_edit.dart
index 901774dcb..a439ef036 100644
--- a/lib/ui/payment/edit/payment_edit.dart
+++ b/lib/ui/payment/edit/payment_edit.dart
@@ -211,7 +211,7 @@ class _PaymentEditState extends State<PaymentEdit> {
                   entityType: EntityType.client,
                   labelText: AppLocalization.of(context)!.client,
                   entityId: payment.clientId,
-                  validator: (String val) => val.trim().isEmpty
+                  validator: (String? val) => (val ?? '').trim().isEmpty
                       ? AppLocalization.of(context)!.pleaseSelectAClient
                       : null,
                   onSelected: (client) {
diff --git a/lib/ui/project/edit/project_edit.dart b/lib/ui/project/edit/project_edit.dart
index e21af9e78..9ebabc367 100644
--- a/lib/ui/project/edit/project_edit.dart
+++ b/lib/ui/project/edit/project_edit.dart
@@ -168,7 +168,7 @@ class _ProjectEditState extends State<ProjectEdit> {
                               state.clientState.list,
                               state.userState.map,
                               state.staticState),
-                          validator: (String val) => val.trim().isEmpty
+                          validator: (String? val) => (val ?? '').trim().isEmpty
                               ? localization.pleaseSelectAClient
                               : null,
                           onSelected: (client) {