diff --git a/src/starfile/parser.py b/src/starfile/parser.py
index 567a885..4de697d 100644
--- a/src/starfile/parser.py
+++ b/src/starfile/parser.py
@@ -15,6 +15,11 @@
 if TYPE_CHECKING:
     from os import PathLike
 
+def _apply_numeric(col: pd.Series) -> pd.Series:
+    try:
+        return pd.to_numeric(col)
+    except ValueError:
+        return col
 
 class StarParser:
     filename: Path
@@ -110,9 +115,9 @@ def _parse_loop_block(self) -> pd.DataFrame:
                 comment='#',
                 keep_default_na=False
             )
-            df_numeric = df.apply(pd.to_numeric, errors='ignore')
+            df_numeric = df.apply(_apply_numeric)
             # Replace columns that are all NaN with the original string columns
-            df_numeric.loc[:, df_numeric.isna().all()] = df.loc[:, df_numeric.isna().all()]
+            df_numeric[df_numeric.columns[df_numeric.isna().all()]] = df[df_numeric.columns[df_numeric.isna().all()]]
             df = df_numeric
             df.columns = loop_column_names
         return df