diff --git a/datafusion/spark/src/function/datetime/next_day.rs b/datafusion/spark/src/function/datetime/next_day.rs
index 2241043d44cd..110dbe432c64 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"),
diff --git a/datafusion/sqllogictest/test_files/spark/datetime/next_day.slt b/datafusion/sqllogictest/test_files/spark/datetime/next_day.slt
index 872d1f2b58eb..e81e76fabf77 100644
--- a/datafusion/sqllogictest/test_files/spark/datetime/next_day.slt
+++ b/datafusion/sqllogictest/test_files/spark/datetime/next_day.slt
@@ -64,6 +64,22 @@ SELECT next_day('2020-01-01'::DATE, 'invalid_day'::string);
 ----
 NULL
 
+# Whitespace must NOT be trimmed — Spark does not accept padded day names (issue #22717)
+query D
+SELECT next_day('2024-01-01'::DATE, ' MO '::string);
+----
+NULL
+
+query D
+SELECT next_day('2024-01-01'::DATE, ' Monday '::string);
+----
+NULL
+
+query D
+SELECT next_day('2024-01-01'::DATE, '  sun  '::string);
+----
+NULL
+
 query error Cast error: Cannot cast string '2015-13-32' to value of Date32 type
 SELECT next_day('2015-13-32'::DATE, 'Sun'::string);