diff --git a/cash/admin.py b/cash/admin.py
index bd6ec30..a61c9ca 100644
--- a/cash/admin.py
+++ b/cash/admin.py
@@ -103,7 +103,7 @@ class SalesLogEntryAdmin(admin.ModelAdmin):
 	list_display = ('account', 'timestamp', 'product', 'count', 'unit_price')
 	list_filter = ['account', 'timestamp', 'product']
 	# Make sales log entries completely read-only
-	readonly_fields = SalesLogEntry._meta.get_all_field_names()
+	readonly_fields = map(lambda f: f.name, SalesLogEntry._meta.fields)
 
 class TransactionAdmin(admin.ModelAdmin):
 	list_display = ('account', 'timestamp', 'subject', 'description', 'amount')