diff --git a/src/ocrmypdf/cli.py b/src/ocrmypdf/cli.py
index a34a2108..fd76f7cc 100644
--- a/src/ocrmypdf/cli.py
+++ b/src/ocrmypdf/cli.py
@@ -63,7 +63,7 @@ class LanguageSetAction(argparse.Action):
     def __call__(self, parser, namespace, values, option_string=None):
         dest = getattr(namespace, self.dest)
         if '+' in values:
-            dest.add(lang for lang in values.split('+'))
+            dest.update(lang for lang in values.split('+'))
         else:
             dest.add(values)
 
diff --git a/tests/test_main.py b/tests/test_main.py
index 289cbbcc..5df4a703 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -875,3 +875,8 @@ def test_image_dpi_not_image(caplog, resources, outpdf):
         'tests/plugins/tesseract_noop.py',
     )
     assert '--image-dpi is being ignored' in caplog.text
+
+
+def test_two_languages(resources, no_outpdf):
+    p, _, _ = run_ocrmypdf(resources / 'graph_ocred.pdf', no_outpdf, '-l', 'eng+deu')
+    assert p.returncode == ExitCode.already_done_ocr