diff --git a/vortex-datetime-parts/src/compute.rs b/vortex-datetime-parts/src/compute.rs
index c21843e833..4a525af07f 100644
--- a/vortex-datetime-parts/src/compute.rs
+++ b/vortex-datetime-parts/src/compute.rs
@@ -159,7 +159,7 @@ impl AsContiguousFn for DateTimePartsArray {
             vortex_bail!(ComputeError: "mismatched dtypes in call to as_contiguous");
         }
 
-        let mut chunks = Vec::with_capacity(arrays.iter().map(|array| array.len()).sum());
+        let mut chunks = Vec::with_capacity(arrays.len());
 
         for array in arrays {
             let dt_parts = Self::try_from(array)?;