The current path, search_shop/5ka/, didn't match any of these. Django

I have an error:

The current path, search_shop/5ka/, didn't match any of these.

Reason of the problem is name of the slug field 5ka. When I changed name from 5ka to pka it works fine.

How can I use 5ka without errors?

models.py

class Shop(models.Model):
    title = models.CharField(max_length=200)
    image = models.ImageField(blank=True)
    slug = models.SlugField(null=False, default="Shop") # I mean this field

def get_search_url(self):
    return reverse('search_shop', kwargs={'slug': self.slug})

urls.py

urlpatterns = [
    path('', HomePageView.as_view(), name='main_list'),
    path('search/', SearchResultsView.as_view(), name='search_results'),
    path('search_shop/<slug:slug>', ProductListView.as_view(), name='search_shop'),
    path('search_shop_results/<slug:slug>/', ProductSearchResultsView.as_view(), name='search_shop_results'),
    path('<slug:slug>/<int:pk>/', views.product_detail, name='product_detail'),

    path('shops/', ShopListView.as_view(), name='shop_list'),
]

shop_list.html

{% for shop in shops %}   
    <a href="{{ shop.get_search_url }}"