Use Apache Spark 2.3.4 as default release version
diff --git a/Dockerfile b/Dockerfile
index 07a8bfc..bd409ea 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -26,7 +26,7 @@
     npm install -g bower
 
 # for Apache Spark demos
-ENV APACHE_SPARK_VERSION 2.2.0
+ENV APACHE_SPARK_VERSION 2.3.4
 
 RUN apt-get -y update && \
     apt-get -y install software-properties-common
diff --git a/Dockerfile.system-test b/Dockerfile.system-test
index e8e1cff..d3dbcec 100644
--- a/Dockerfile.system-test
+++ b/Dockerfile.system-test
@@ -23,7 +23,7 @@
 USER root
 
 # Spark dependencies
-ENV APACHE_SPARK_VERSION 2.3.3
+ENV APACHE_SPARK_VERSION 2.3.4
 
 RUN apt-get -y update && \
     apt-get install -y --no-install-recommends openjdk-8-jre-headless && \
diff --git a/Makefile b/Makefile
index dddf927..057136a 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,7 @@
 SNAPSHOT:=-SNAPSHOT
 endif
 
-APACHE_SPARK_VERSION?=2.2.2
+APACHE_SPARK_VERSION?=2.3.4
 SCALA_VERSION?=2.11
 IMAGE?=jupyter/all-spark-notebook:228ae7a44e0c
 EXAMPLE_IMAGE?=apache/toree-examples