diff --git a/fesod-common/src/main/java/org/apache/fesod/common/util/StringUtils.java b/fesod-common/src/main/java/org/apache/fesod/common/util/StringUtils.java
index abd801601b..ba71176c5f 100644
--- a/fesod-common/src/main/java/org/apache/fesod/common/util/StringUtils.java
+++ b/fesod-common/src/main/java/org/apache/fesod/common/util/StringUtils.java
@@ -198,8 +198,9 @@ public static boolean regionMatches(
             }
 
             // The same check as in String.regionMatches():
-            if (Character.toUpperCase(c1) != Character.toUpperCase(c2)
-                    && Character.toLowerCase(c1) != Character.toLowerCase(c2)) {
+            final char upper1 = Character.toUpperCase(c1);
+            final char upper2 = Character.toUpperCase(c2);
+            if (upper1 != upper2 && Character.toLowerCase(upper1) != Character.toLowerCase(upper2)) {
                 return false;
             }
         }
diff --git a/fesod-common/src/test/java/org/apache/fesod/common/util/StringUtilsTest.java b/fesod-common/src/test/java/org/apache/fesod/common/util/StringUtilsTest.java
index 0f4ec3d0a4..52432b99c9 100644
--- a/fesod-common/src/test/java/org/apache/fesod/common/util/StringUtilsTest.java
+++ b/fesod-common/src/test/java/org/apache/fesod/common/util/StringUtilsTest.java
@@ -211,6 +211,28 @@ boolean invoke() {
         }
     }
 
+    @Test
+    void test_regionMatches_unicodeIgnoreCase() {
+        final CharSequence[] dottedI = {"İ", new StringBuilder("İ")};
+        final CharSequence[] dotlessI = {"ı", new StringBuilder("ı")};
+        for (final CharSequence source : dottedI) {
+            for (final CharSequence other : dotlessI) {
+                Assertions.assertEquals(
+                        source.toString().regionMatches(true, 0, other.toString(), 0, 1),
+                        StringUtils.regionMatches(source, true, 0, other, 0, 1));
+                Assertions.assertEquals(
+                        other.toString().regionMatches(true, 0, source.toString(), 0, 1),
+                        StringUtils.regionMatches(other, true, 0, source, 0, 1));
+                Assertions.assertEquals(
+                        source.toString().regionMatches(false, 0, other.toString(), 0, 1),
+                        StringUtils.regionMatches(source, false, 0, other, 0, 1));
+                Assertions.assertEquals(
+                        other.toString().regionMatches(false, 0, source.toString(), 0, 1),
+                        StringUtils.regionMatches(other, false, 0, source, 0, 1));
+            }
+        }
+    }
+
     @Test
     void stripTest() {
         Assertions.assertNull(StringUtils.strip(null));