diff --git a/spark/Dockerfile b/spark/Dockerfile
index 41ca8c0..1dcea14 100644
--- a/spark/Dockerfile
+++ b/spark/Dockerfile
@@ -1,8 +1,8 @@
 FROM python:3.6-alpine3.9
 
-ENV SPARK_VERSION 2.4.3
-ENV SPARK_INSTALL /usr/local
-ENV HADOOP_VERSION 2.7
+ENV SPARK_VERSION="2.4.3" \
+    HADOOP_VERSION="2.7" \
+    SPARK_INSTALL="/usr/local"
 
 RUN apk add --no-cache \
         bash \
@@ -22,11 +22,11 @@
 COPY start-master.sh /usr/local/bin/start-master.sh
 COPY start-worker.sh /usr/local/bin/start-worker.sh
 
-ENV SPARK_HOME $SPARK_INSTALL/spark
-ENV SPARK_LOCAL_IP 127.0.0.1
-ENV SPARK_MASTER_PORT 7077
-ENV SPARK_MASTER_WEBUI_PORT 8080
-ENV PYSPARK_PYTHON /usr/local/bin/python3
+ENV SPARK_HOME="$SPARK_INSTALL/spark" \
+    SPARK_LOCAL_IP="127.0.0.1" \
+    SPARK_MASTER_PORT="7077" \
+    SPARK_MASTER_WEBUI_PORT="8080" \
+    PYSPARK_PYTHON="/usr/local/bin/python3"
 
 # Spark doesn't seem to respond directly to SIGTERM as the exit status is
 # for SIGKILL (137), after a pause. Presumably docker-compose down times out.