diff --git a/xos/core/models/plcorebase.py b/xos/core/models/plcorebase.py
index 238e6f0..a5f73e5 100644
--- a/xos/core/models/plcorebase.py
+++ b/xos/core/models/plcorebase.py
@@ -192,12 +192,12 @@
 
     def check_composite_primary_key(self):
         try:
-            composite_key_exists = self.composite_primary_key
+            composite_key_exists = (self.composite_primary_key!=None) and (self.composite_primary_key!=[])
         except AttributeError:
             composite_key_exists = False
 
-            if (not composite_key_exists):
-                return
+        if (not composite_key_exists):
+            return
 
         # dictionary containing cpk field name and value
         cpk_fields = dict([(name, getattr(self, name)) for name in self.composite_primary_key])