diff --git a/dpdata/plugins/openmx.py b/dpdata/plugins/openmx.py
index f340857cb..121828c27 100644
--- a/dpdata/plugins/openmx.py
+++ b/dpdata/plugins/openmx.py
@@ -3,7 +3,7 @@
 from dpdata.format import Format
 
 
-@Format.register("openmx")
+@Format.register("openmx/out")
 class OPENMXFormat(Format):
     """Format for the `OpenMX <https://www.openmx-square.org/>`.
 
diff --git a/tests/test_openmx.py b/tests/test_openmx.py
index 5d4de3da8..90bf38240 100644
--- a/tests/test_openmx.py
+++ b/tests/test_openmx.py
@@ -50,12 +50,12 @@ def test_coord(self):
 
 class TestOPENMXTraj(unittest.TestCase, TestOPENMXTRAJProps):
     def setUp(self):
-        self.system = dpdata.System("openmx/Methane", fmt="openmx")
+        self.system = dpdata.System("openmx/Methane", fmt="openmx/out")
 
 
 class TestOPENMXLabeledTraj(unittest.TestCase, TestOPENMXTRAJProps):
     def setUp(self):
-        self.system = dpdata.LabeledSystem("openmx/Methane", fmt="openmx")
+        self.system = dpdata.LabeledSystem("openmx/Methane", fmt="openmx/out")
 
 
 if __name__ == "__main__":