diff --git a/swvo/io/omni/omni_high_res.py b/swvo/io/omni/omni_high_res.py
index 5d1476b..0b16f7f 100644
--- a/swvo/io/omni/omni_high_res.py
+++ b/swvo/io/omni/omni_high_res.py
@@ -288,6 +288,7 @@ def _process_single_year(self, data: list[str]) -> pd.DataFrame:
             "proton_density": 999.8,
             "temperature": 9999998.0,
             "pdyn": 99.0,
+            "sym-h": 99999.0,
         }
 
         df.columns = maxes.keys()