diff --git a/e2e.sh b/e2e.sh
index a13e67abd..7443f6517 100755
--- a/e2e.sh
+++ b/e2e.sh
@@ -4,7 +4,7 @@ SCALA_VERSION=${SCALA_VERSION:-${TRAVIS_SCALA_VERSION:-2.11.11}}
 
 # E2E_SHADED signals we will work with the shaded version of the
 # compilerplugin.
-if [ $E2E_SHADED = "1" ]; then
+if [ "$E2E_SHADED" = "1" ]; then
   mv e2e/project/scalapb.sbt.shaded e2e/project/scalapb.sbt
 fi