diff --git a/cli/config.py b/cli/config.py
index 20184c7c..6bd924ed 100644
--- a/cli/config.py
+++ b/cli/config.py
@@ -325,7 +325,7 @@ def _merge_dict(self, config):
             self.spark_defaults_conf = self.__convert_to_path(spark_configuration.get('spark_defaults_conf'))
             self.spark_env_sh = self.__convert_to_path(spark_configuration.get('spark_env_sh'))
             self.core_site_xml = self.__convert_to_path(spark_configuration.get('core_site_xml'))
-            self.jars = [self.__convert_to_path(jar) for jar in spark_configuration.get('jars')]
+            self.jars = [self.__convert_to_path(jar) for jar in spark_configuration.get('jars') or []]
 
     def __convert_to_path(self, str_path):
         if str_path:
diff --git a/config/spark-defaults.conf b/config/spark-defaults.conf
index 683b41aa..89e178e7 100644
--- a/config/spark-defaults.conf
+++ b/config/spark-defaults.conf
@@ -35,4 +35,8 @@ spark.jars                      /home/spark-current/jars/azure-storage-2.0.0.jar
 spark.deploy.recoveryMode       FILESYSTEM
 spark.deploy.recoveryDirectory  /root/
 
+# enable spark shuffle service
 spark.shuffle.service.enabled   true
+
+# enable dynamic allocation
+spark.dynamicAllocation.enabled true