diff --git a/.travis.sh b/.travis.sh
index bcd7c79ed..24e9f33d8 100755
--- a/.travis.sh
+++ b/.travis.sh
@@ -49,7 +49,7 @@ if [ "$TRAVIS_BRANCH" == "master" -a "$TRAVIS_PULL_REQUEST" == "false" ]; then
   # Set configuration for repository and deploy documentation
   git config --global user.name "${GH_NAME}"
   git config --global user.email "${GH_EMAIL}"
-  git remote set-url origin $REMOTE
+  git remote set-url origin ${REMOTE}
 
   # Install GitHub pages import helper and Material, so we can use it as a
   # base template and add overrides
@@ -65,7 +65,7 @@ fi
 rm -rf overrides
 
 # Terminate if we're not on a release branch
-echo "$TRAVIS_BRANCH" | grep -qvE "^[0-9.]+$" && exit 0; :;
+echo "${TRAVIS_BRANCH}" | grep -qvE "^[0-9.]+$" && exit 0; :;
 
 # Install dependencies for release build
 pip install --user wheel twine
@@ -76,23 +76,23 @@ pip install --user urllib3[secure]
 
 # Build and install theme and Docker image
 python setup.py build sdist bdist_wheel --universal
-docker build -t $TRAVIS_REPO_SLUG .
+docker build -t ${TRAVIS_REPO_SLUG} .
 
 # Prepare build regression test
 pushd /tmp
 mkdocs new test && cd test
 
 # Test Docker image build
-docker run --rm -it -v $(pwd):/docs $TRAVIS_REPO_SLUG build --theme material
+docker run --rm -it -v $(pwd):/docs ${TRAVIS_REPO_SLUG} build --theme material
 
 # Return to original directory
 popd
 
 # Push release to PyPI
-twine upload -u $PYPI_USERNAME -p $PYPI_PASSWORD dist/*
+twine upload -u ${PYPI_USERNAME} -p ${PYPI_PASSWORD} dist/*
 
 # Push image to Docker Hub
-docker login -u $DOCKER_USERNAME -p $DOCKER_PASSWORD
-docker tag $TRAVIS_REPO_SLUG $TRAVIS_REPO_SLUG:$TRAVIS_BRANCH
-docker tag $TRAVIS_REPO_SLUG $TRAVIS_REPO_SLUG:latest
-docker push $TRAVIS_REPO_SLUG
+docker login -u ${DOCKER_USERNAME} -p ${DOCKER_PASSWORD}
+docker tag ${TRAVIS_REPO_SLUG} ${TRAVIS_REPO_SLUG}:${TRAVIS_BRANCH}
+docker tag ${TRAVIS_REPO_SLUG} ${TRAVIS_REPO_SLUG}:latest
+docker push ${TRAVIS_REPO_SLUG}