diff --git a/ram/bookshelf/models.py b/ram/bookshelf/models.py
index fba7aa5..3469a31 100644
--- a/ram/bookshelf/models.py
+++ b/ram/bookshelf/models.py
@@ -137,6 +137,10 @@ class Catalog(BaseBook):
         ordering = ["manufacturer", "publication_year"]
 
     def __str__(self):
+        # if the object is new, return an empty string to avoid
+        # calling self.scales.all() which would raise a infinite recursion
+        if self.pk is None:
+            return str()  # empty string
         scales = self.get_scales()
         return "%s %s %s" % (self.manufacturer.name, self.years, scales)
 
diff --git a/ram/ram/__init__.py b/ram/ram/__init__.py
index abac0a2..c84cd75 100644
--- a/ram/ram/__init__.py
+++ b/ram/ram/__init__.py
@@ -1,4 +1,4 @@
 from ram.utils import git_suffix
 
-__version__ = "0.17.2"
+__version__ = "0.17.3"
 __version__ += git_suffix(__file__)
diff --git a/ram/roster/admin.py b/ram/roster/admin.py
index f1962aa..7c79b75 100644
--- a/ram/roster/admin.py
+++ b/ram/roster/admin.py
@@ -273,11 +273,11 @@ class RollingStockAdmin(SortableAdminBase, admin.ModelAdmin):
                     settings.CSV_SEPARATOR_ALT.join(
                         t.name for t in obj.tags.all()
                     ),
-                    obj.decoder_interface,
+                    obj.get_decoder_interface_display(),
                     obj.decoder,
                     obj.address,
-                    obj.purchase_date,
                     obj.shop,
+                    obj.purchase_date,
                     obj.price,
                     properties,
                 ]