diff --git a/moto/dynamodb2/models.py b/moto/dynamodb2/models.py
index e9980410b..2c6d8d60f 100644
--- a/moto/dynamodb2/models.py
+++ b/moto/dynamodb2/models.py
@@ -119,9 +119,9 @@ class Item(object):
                 value = value.lstrip(":").rstrip(",")
                 for k, v in expression_attribute_names.items():
                     value = value.replace(k, v)
-                if action == "REMOVE" or action == 'remove':
+                if action == "REMOVE":
                     self.attrs.pop(value, None)
-                elif action == 'SET' or action == 'set':
+                elif action == 'SET':
                     key, value = value.split("=")
                     key = key.strip()
                     value = value.strip()
@@ -129,6 +129,8 @@ class Item(object):
                         self.attrs[key] = DynamoType(expression_attribute_values[value])
                     else:
                         self.attrs[key] = DynamoType({"S": value})
+                else:
+                    raise NotImplementedError('{} update action not yet supported'.format(action))
 
     def update_with_attribute_updates(self, attribute_updates):
         for attribute_name, update_action in attribute_updates.items():
@@ -323,7 +325,6 @@ class Table(object):
     def query(self, hash_key, range_comparison, range_objs, limit,
               exclusive_start_key, scan_index_forward, index_name=None, **filter_kwargs):
         results = []
-
         if index_name:
             all_indexes = (self.global_indexes or []) + (self.indexes or [])
             indexes_by_name = dict((i['IndexName'], i) for i in all_indexes)
diff --git a/moto/dynamodb2/responses.py b/moto/dynamodb2/responses.py
index 081afc2c4..eea2bace5 100644
--- a/moto/dynamodb2/responses.py
+++ b/moto/dynamodb2/responses.py
@@ -279,19 +279,22 @@ class DynamoHandler(BaseResponse):
             else:
                 index = table.schema
 
-            key_map = [column for _, column in sorted((k, v) for k, v in self.body['ExpressionAttributeNames'].items())]
+            reverse_attribute_lookup = {v: k for k, v in self.body['ExpressionAttributeNames'].iteritems()}
 
             if " AND " in key_condition_expression:
                 expressions = key_condition_expression.split(" AND ", 1)
 
                 index_hash_key = [key for key in index if key['KeyType'] == 'HASH'][0]
-                hash_key_index_in_key_map = key_map.index(index_hash_key['AttributeName'])
+                hash_key_var = reverse_attribute_lookup.get(index_hash_key['AttributeName'], index_hash_key['AttributeName'])
+                i, hash_key_expression = ((i, e) for i, e in enumerate(expressions) if re.search(r'[\s(]#n1\b'.format(hash_key_var), e)).next()
+                hash_key_expression = hash_key_expression.strip('()')
+                expressions.pop(i)
 
-                hash_key_expression = expressions.pop(hash_key_index_in_key_map).strip('()')
                 # TODO implement more than one range expression and OR operators
                 range_key_expression = expressions[0].strip('()')
                 range_key_expression_components = range_key_expression.split()
                 range_comparison = range_key_expression_components[1]
+
                 if 'AND' in range_key_expression:
                     range_comparison = 'BETWEEN'
                     range_values = [