diff --git a/saqc/__main__.py b/saqc/__main__.py
index 9d1738b74a58c436ca0c76e75de7943176a14e9f..4aea86013379c4e6e46062f396a94c266e170a10 100644
--- a/saqc/__main__.py
+++ b/saqc/__main__.py
@@ -157,7 +157,7 @@ def main(
                 flagscol = flagscol.rename("flags")
             out[k] = pd.concat([data_result[k].rename("data"), flagscol], axis=1)
 
-        writeData(writer, out.to_pandas(), outfile)
+        writeData(writer, out.to_pandas(fill_value=-9999 if scheme == "positional" else np.nan), outfile)
 
 
 if __name__ == "__main__":
diff --git a/tests/cli/test_integration.py b/tests/cli/test_integration.py
index 0971c44b8bc8d4bb9be8ca22137a9e0b59ba7805..a2cf2a70c2bb5113142370330709f0736c0e1b69 100644
--- a/tests/cli/test_integration.py
+++ b/tests/cli/test_integration.py
@@ -38,13 +38,13 @@ POSITIONAL = [
     ",Battery,Battery,SM1,SM1,SM2,SM2\n",
     ",data,flags,data,flags,data,flags\n",
     "Date,,,,,,\n",
-    "2016-04-01 00:00:00,nan,-9999,nan,-9999,29.3157,90000\n",
-    "2016-04-01 00:05:48,3573.0,9,32.685,90,nan,-9999\n",
-    "2016-04-01 00:15:00,nan,-9999,nan,-9999,29.3157,90000\n",
-    "2016-04-01 00:20:42,3572.0,9,32.7428,90,nan,-9999\n",
-    "2016-04-01 00:30:00,nan,-9999,nan,-9999,29.3679,90002\n",
-    "2016-04-01 00:35:37,3572.0,9,32.6186,90,nan,-9999\n",
-    "2016-04-01 00:45:00,nan,-9999,nan,-9999,29.3679,90000\n",
+    "2016-04-01 00:00:00,-9999,-9999,-9999.0,-9999,29.3157,90000\n",
+    "2016-04-01 00:05:48,3573,9,32.685,90,-9999.0,-9999\n",
+    "2016-04-01 00:15:00,-9999,-9999,-9999.0,-9999,29.3157,90000\n",
+    "2016-04-01 00:20:42,3572,9,32.7428,90,-9999.0,-9999\n",
+    "2016-04-01 00:30:00,-9999,-9999,-9999.0,-9999,29.3679,90002\n",
+    "2016-04-01 00:35:37,3572,9,32.6186,90,-9999.0,-9999\n",
+    "2016-04-01 00:45:00,-9999,-9999,-9999.0,-9999,29.3679,90000\n",
 ]
 
 DMP = [
@@ -91,5 +91,4 @@ def test__main__py(tmp_path, scheme, expected):
     assert result.exit_code == 0, result.output
     with open(outfile, "r") as f:
         result = f.readlines()[:10]
-        print(result[4])
-        # assert result == expected
+        assert result == expected