diff --git a/monetio/obs/aqs.py b/monetio/obs/aqs.py
index b20ca3bd..503c22d5 100644
--- a/monetio/obs/aqs.py
+++ b/monetio/obs/aqs.py
@@ -562,7 +562,7 @@ def add_data2(self, df, daily=False, network=None):
                 }
             )
         if network is not None:
-            self.df = self.df.dropna(subset="networks")
+            self.df = self.df.dropna(subset=["networks"])
         # if daily:
         #     self.df["time"] = self.df.time_local - pd.to_timedelta(self.df.gmt_offset, unit="H")
         if pd.Series(self.df.columns).isin(["parameter_name"]).max():