diff --git a/InvenTree/build/serializers.py b/InvenTree/build/serializers.py
index 7df2c474a9..d037ad546e 100644
--- a/InvenTree/build/serializers.py
+++ b/InvenTree/build/serializers.py
@@ -630,6 +630,7 @@ class BuildAllocationItemSerializer(serializers.Serializer):
 
         super().validate(data)
 
+        build = self.context['build']
         bom_item = data['bom_item']
         stock_item = data['stock_item']
         quantity = data['quantity']
@@ -654,16 +655,20 @@ class BuildAllocationItemSerializer(serializers.Serializer):
         # Output *must* be set for trackable parts
         if output is None and bom_item.sub_part.trackable:
             raise ValidationError({
-                'output': _('Build output must be specified for allocation of tracked parts')
+                'output': _('Build output must be specified for allocation of tracked parts'),
             })
 
         # Output *cannot* be set for un-tracked parts
         if output is not None and not bom_item.sub_part.trackable:
 
             raise ValidationError({
-                'output': _('Build output cannot be specified for allocation of untracked parts')
+                'output': _('Build output cannot be specified for allocation of untracked parts'),
             })
 
+        # Check if this allocation would be unique
+        if BuildItem.objects.filter(build=build, stock_item=stock_item, install_into=output).exists():
+            raise ValidationError(_('This stock item has already been allocated to this build output'))
+
         return data
 
 
diff --git a/InvenTree/templates/js/translated/build.js b/InvenTree/templates/js/translated/build.js
index 705060ce63..c996501060 100644
--- a/InvenTree/templates/js/translated/build.js
+++ b/InvenTree/templates/js/translated/build.js
@@ -1982,7 +1982,7 @@ function allocateStockToBuild(build_id, part_id, bom_items, options={}) {
         // var stock_input = constructRelatedFieldInput(`items_stock_item_${pk}`);
 
         var html = `
-        <tr id='allocation_row_${pk}' class='part-allocation-row'>
+        <tr id='items_${pk}' class='part-allocation-row'>
             <td id='part_${pk}'>
                 ${thumb} ${sub_part.full_name}
             </td>
@@ -2167,7 +2167,7 @@ function allocateStockToBuild(build_id, part_id, bom_items, options={}) {
             $(options.modal).find('.button-row-remove').click(function() {
                 var pk = $(this).attr('pk');
 
-                $(options.modal).find(`#allocation_row_${pk}`).remove();
+                $(options.modal).find(`#items_${pk}`).remove();
             });
         },
         onSubmit: function(fields, opts) {