diff --git a/ci/before_install_jython.sh b/ci/before_install_jython.sh
index 491d3ad..d32ce5f 100755
--- a/ci/before_install_jython.sh
+++ b/ci/before_install_jython.sh
@@ -6,6 +6,6 @@ if [ ! -d "$INST_DIR" ]; then
     JYTHON_JAR=$(${TRAVIS_BUILD_DIR}/ci/mvnget.sh "$JYTHON")
     java -jar ${JYTHON_JAR} -s -d "$INST_DIR"
 fi
-pip install --upgrade virtualenv==16.5.0
+pip install --upgrade virtualenv==15.0.1
 mkdir -p $HOME/bin
 ln -s "$INST_DIR"/bin/jython $HOME/bin/