diff --git a/src/ocrd_utils/logging.py b/src/ocrd_utils/logging.py
index addd1cfca..7fede27c9 100644
--- a/src/ocrd_utils/logging.py
+++ b/src/ocrd_utils/logging.py
@@ -205,3 +205,8 @@ def disableLogging(silent=not config.OCRD_LOGGING_DEBUG):
     # Python default log level is WARNING
     logging.root.setLevel(logging.WARNING)
 
+# Initialize logging now to prevent any other libraries (tensorflow,
+# matplotlib ...) from adding their own root handler, which might mangle the
+# STDOUT (our logging will log to STDERR so as not to interfere with
+# --dump-json etc.)
+initLogging()
diff --git a/tests/cli/test_log.py b/tests/cli/test_log.py
index 3d81e8266..25db78f5e 100644
--- a/tests/cli/test_log.py
+++ b/tests/cli/test_log.py
@@ -24,6 +24,7 @@ def _get_log_output(self, *args):
 
     def setUp(self):
         super().setUp()
+        disableLogging()
         initLogging()
 
     def tearDown(self):