diff --git a/src/speccpu/__init__.py b/src/speccpu/__init__.py
index abc2f72..3e01cac 100644
--- a/src/speccpu/__init__.py
+++ b/src/speccpu/__init__.py
@@ -114,7 +114,7 @@ class SPEC:
             workload,
             "-c",
             config,
-            *(["--outputdir", str(output_root)] if output_root else []),
+            *(["--output_root", str(output_root)] if output_root else []),
             *benchmarks,
         ]
 
diff --git a/test/test_spec.py b/test/test_spec.py
index 77599f3..b5579ea 100644
--- a/test/test_spec.py
+++ b/test/test_spec.py
@@ -77,7 +77,7 @@ class TestSPEC:
         spec = SPEC(Path("/path/to/spec"))
         output_dir = Path("/output/dir")
         cmd = spec.mkcmd_runcpu("myconfig", ["benchmark1"], output_root=output_dir)
-        assert "--outputdir" in cmd
+        assert "--output_root" in cmd
         assert str(output_dir) in cmd