diff --git a/packages/devextreme/js/__internal/data/m_array_query.ts b/packages/devextreme/js/__internal/data/m_array_query.ts
index b308ee8a8fe7..cdb326386a0f 100644
--- a/packages/devextreme/js/__internal/data/m_array_query.ts
+++ b/packages/devextreme/js/__internal/data/m_array_query.ts
@@ -249,7 +249,7 @@ const SortIterator = Iterator.inherit({
 const compileCriteria = (function () {
   let langParams = {};
   // eslint-disable-next-line @typescript-eslint/naming-convention
-  const _toComparable = (value) => toComparable(value, false, langParams);
+  const _toComparable = (value) => toComparable(value, false, langParams, { useUpperCase: true });
 
   const compileUniformEqualsCriteria = (crit) => {
     const getter = compileGetter(crit[0][0]);
diff --git a/packages/devextreme/js/core/utils/data.js b/packages/devextreme/js/core/utils/data.js
index 11fb29ec699d..6ae61e02f3b1 100644
--- a/packages/devextreme/js/core/utils/data.js
+++ b/packages/devextreme/js/core/utils/data.js
@@ -138,6 +138,14 @@ function combineGetters(getters) {
     };
 }
 
+function toLowerCase(value, options) {
+    return options?.locale ? value.toLocaleLowerCase(options.locale) : value.toLowerCase();
+}
+
+function toUpperCase(value, options) {
+    return options?.locale ? value.toLocaleUpperCase(options.locale) : value.toUpperCase();
+}
+
 const ensurePropValueDefined = function(obj, propName, value, options) {
     if(isDefined(value)) {
         return value;
@@ -181,27 +189,27 @@ export const compileSetter = function(expr) {
     };
 };
 
-export const toComparable = function(value, caseSensitive, options = {}) {
+export const toComparable = function(value, caseSensitive, langParams = {}, options = { useUpperCase: false }) {
     if(value instanceof Date) {
         return value.getTime();
     }
 
-    if(value && value instanceof Class && value.valueOf) {
-        return value.valueOf();
-    }
+    const collatorSensitivity = langParams?.collatorOptions?.sensitivity;
 
-    const collatorSensitivity = options?.collatorOptions?.sensitivity;
-
-    if(typeof value === 'string' && collatorSensitivity === 'base') {
+    if(value && value instanceof Class && value.valueOf) {
+        value = value.valueOf();
+    } else if(typeof value === 'string' && collatorSensitivity === 'base') {
         const REMOVE_DIACRITICAL_MARKS_REGEXP = /[\u0300-\u036f]/g;
 
         value = value.normalize('NFD').replace(REMOVE_DIACRITICAL_MARKS_REGEXP, '');
     }
 
-    const isCaseSensitive = collatorSensitivity === 'case' || caseSensitive;
+    const isCaseSensitive = caseSensitive || collatorSensitivity === 'case';
 
     if(typeof value === 'string' && !isCaseSensitive) {
-        return options?.locale ? value.toLocaleUpperCase(options.locale) : value.toUpperCase();
+        return options?.useUpperCase ?
+            toUpperCase(value, langParams)
+            : toLowerCase(value, langParams);
     }
 
     return value;
diff --git a/packages/devextreme/testing/tests/DevExpress.data/queryArray.tests.js b/packages/devextreme/testing/tests/DevExpress.data/queryArray.tests.js
index 0ecda45083af..611142c0bf4b 100644
--- a/packages/devextreme/testing/tests/DevExpress.data/queryArray.tests.js
+++ b/packages/devextreme/testing/tests/DevExpress.data/queryArray.tests.js
@@ -430,6 +430,17 @@ QUnit.test('filtering use correct case insensitivity search', function(assert) {
     assert.false(containsUnwantedValue);
 });
 
+QUnit.test('filtering use correct case insensitivity search for AM locale', function(assert) {
+    const input = [
+        { ID: 1, Name: 'ԵՐԵՒԱՆ' },
+        { ID: 2, Name: 'Երևան' },
+    ];
+
+    const arrayStartsWith = QUERY(input).filter(['Name', 'startswith', 'Երև']).toArray();
+
+    assert.equal(arrayStartsWith.length, 2);
+});
+
 QUnit.test('missing operation means equal', function(assert) {
     assert.expect(1);