diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/rules/RuleExecutor.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/rules/RuleExecutor.scala
index 183be5a027ec5..e991a2dc7462f 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/rules/RuleExecutor.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/rules/RuleExecutor.scala
@@ -144,7 +144,7 @@ abstract class RuleExecutor[TreeType <: TreeNode[_]] extends Logging {
 
   private class PlanChangeLogger {
 
-    private val logLevel = SQLConf.get.optimizerPlanChangeLogLevel.toUpperCase
+    private val logLevel = SQLConf.get.optimizerPlanChangeLogLevel
 
     private val logRules = SQLConf.get.optimizerPlanChangeRules.map(Utils.stringToSeq)
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
index ddf17fa88c76b..0e0a01def357e 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
@@ -177,8 +177,8 @@ object SQLConf {
       "plan after a rule is applied. The value can be 'trace', 'debug', 'info', 'warn', or " +
       "'error'. The default log level is 'trace'.")
     .stringConf
-    .checkValue(
-      str => Set("TRACE", "DEBUG", "INFO", "WARN", "ERROR").contains(str.toUpperCase),
+    .transform(_.toUpperCase(Locale.ROOT))
+    .checkValue(logLevel => Set("TRACE", "DEBUG", "INFO", "WARN", "ERROR").contains(logLevel),
       "Invalid value for 'spark.sql.optimizer.planChangeLog.level'. Valid values are " +
         "'trace', 'debug', 'info', 'warn' and 'error'.")
     .createWithDefault("trace")