diff --git a/etk/core.py b/etk/core.py
index <HASH>..<HASH> 100644
--- a/etk/core.py
+++ b/etk/core.py
@@ -581,9 +581,10 @@ class Core(object):
             if 'key' in extraction:
                 key = extraction['key']
 
-            if key not in doc[_KNOWLEDGE_GRAPH][field_name]:
-                doc[_KNOWLEDGE_GRAPH][field_name][key] = list()
-            doc[_KNOWLEDGE_GRAPH][field_name][key].append(extraction)
+            if len(key) < 32766:
+                if key not in doc[_KNOWLEDGE_GRAPH][field_name]:
+                    doc[_KNOWLEDGE_GRAPH][field_name][key] = list()
+                doc[_KNOWLEDGE_GRAPH][field_name][key].append(extraction)
 
         return doc
if key is > <I>k throw the extraction