diff --git a/.travis.yml b/.travis.yml
index 36d60b963a1..5bf78eb6532 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -50,7 +50,7 @@ matrix:
     - env: NAME="Doc"
            MAIN_CMD="cd package && python setup.py"
            SETUP_CMD="build_sphinx"
-	   PYTHON_VERSION=3.7
+           PYTHON_VERSION=3.7
            BUILD_DOCS=true
            BUILD_CMD="cd ${TRAVIS_BUILD_DIR}/package && python setup.py build_ext --inplace"
            INSTALL_HOLE="false"