diff --git a/datafusion/spark/src/function/datetime/next_day.rs b/datafusion/spark/src/function/datetime/next_day.rs
index 2241043d44cd7..2ef222526f387 100644
--- a/datafusion/spark/src/function/datetime/next_day.rs
+++ b/datafusion/spark/src/function/datetime/next_day.rs
@@ -210,7 +210,7 @@ where
 fn spark_next_day(days: i32, day_of_week: &str) -> Option<i32> {
     let date = Date32Type::to_naive_date_opt(days)?;
 
-    let day_of_week = day_of_week.trim().to_uppercase();
+    let day_of_week = day_of_week.to_uppercase();
     let day_of_week = match day_of_week.as_str() {
         "MO" | "MON" | "MONDAY" => Some("MONDAY"),
         "TU" | "TUE" | "TUESDAY" => Some("TUESDAY"),
@@ -279,4 +279,10 @@ mod tests {
         assert_eq!(field.data_type(), &DataType::Date32);
         assert!(field.is_nullable());
     }
+
+    #[test]
+    fn next_day_rejects_whitespace_padded_day_names() {
+        let monday = 19723; // 2024-01-01
+        assert_eq!(spark_next_day(monday, " MO "), None);
+    }
 }