diff --git a/debian/rules b/debian/rules
index 9051d5082..bdf2c7321 100755
--- a/debian/rules
+++ b/debian/rules
@@ -19,7 +19,7 @@ override_dh_virtualenv:
 	echo $(PIP_INDEX_URL)
 	dh_virtualenv --index-url $(PIP_INDEX_URL) \
                 --python=/usr/bin/python3.6 \
-		--preinstall cython==0.29.36 \
+                --preinstall cython==0.29.36 \
                 --preinstall pip-custom-platform \
                 --preinstall pip==9.0.1 \
                 --preinstall setuptools==46.1.3 \