diff --git a/tox.ini b/tox.ini
index 65f02ae630e977817d6f677b818fd1729f8e7d44..15ee5c1bf60c437d36818626daea4770cef31515 100644
--- a/tox.ini
+++ b/tox.ini
@@ -7,4 +7,5 @@ deps=pytest
     nose
     pytest-cov
 commands_pre=pip install ../caosdb-pylib/
-commands=pytest --cov=caosdb -vvx {posargs}
+# Add "-x" to stop at first error.
+commands=pytest --cov=caosdb -vv {posargs}