diff --git a/Cargo.toml b/Cargo.toml
index e6e525a1..9beaa0dd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -39,7 +39,7 @@ thiserror = "1.0.25"
 num = "0.4.0"
 float-cmp = "0.9.0"
 ndarray = "0.15.3"
-polars = { version = "0.38.1", features = ["lazy", "rows", "ndarray"] }
+polars = { version = "0.39", features = ["lazy", "rows", "ndarray"] }
 pyo3-polars = "0.12.0"
 pyo3 = { version = "0.20.2", default-features = false }
 pyo3-log = "0.9.0"
diff --git a/pywr-schema/src/timeseries/align_and_resample.rs b/pywr-schema/src/timeseries/align_and_resample.rs
index bbd1830b..e91390c2 100644
--- a/pywr-schema/src/timeseries/align_and_resample.rs
+++ b/pywr-schema/src/timeseries/align_and_resample.rs
@@ -11,12 +11,16 @@ pub fn align_and_resample(
     domain: &ModelDomain,
 ) -> Result<DataFrame, TimeseriesError> {
     // Ensure type of time column is datetime and that it is sorted
+    let sort_options = SortMultipleOptions::default()
+        .with_order_descending(false)
+        .with_maintain_order(true);
+
     let df = df
         .clone()
         .lazy()
         .with_columns([col(time_col).cast(DataType::Datetime(TimeUnit::Nanoseconds, None))])
         .collect()?
-        .sort([time_col], false, true)?;
+        .sort([time_col], sort_options)?;
 
     // Ensure that df start aligns with models start for any resampling
     let df = slice_start(df, time_col, domain)?;