diff --git a/src/question_baseselect.ts b/src/question_baseselect.ts
index 1d3391593e..f55bdcd3d7 100644
--- a/src/question_baseselect.ts
+++ b/src/question_baseselect.ts
@@ -1338,7 +1338,7 @@ export class QuestionSelectBase extends Question {
     for (var i = 0; i < this.dependedQuestions.length; i++) {
       const q = this.dependedQuestions[i];
       q.onVisibleChoicesChanged();
-      q.clearIncorrectValuesCore();
+      q.clearIncorrectValues();
     }
     this.isUpdatingChoicesDependedQuestions = false;
   }
@@ -1426,11 +1426,11 @@ export class QuestionSelectBase extends Question {
   }
   protected clearIncorrectValuesCore() {
     var val = this.value;
-    if (this.canClearValueAnUnknow(val)) {
+    if (this.canClearValueAnUnknown(val)) {
       this.clearValue();
     }
   }
-  protected canClearValueAnUnknow(val: any): boolean {
+  protected canClearValueAnUnknown(val: any): boolean {
     if (!this.getStoreOthersAsComment() && this.isOtherSelected) return false;
     return this.hasUnknownValue(val, true, true, true);
   }
diff --git a/src/question_checkbox.ts b/src/question_checkbox.ts
index 5078831366..a133670469 100644
--- a/src/question_checkbox.ts
+++ b/src/question_checkbox.ts
@@ -260,7 +260,7 @@ export class QuestionCheckboxModel extends QuestionCheckboxBase {
     if (Array.isArray(val)) {
       for (var i = 0; i < val.length; i++) {
         const rVal = this.getRealValue(val[i]);
-        if (this.canClearValueAnUnknow(rVal)) {
+        if (this.canClearValueAnUnknown(rVal)) {
           this.addIntoInvisibleOldValues(rVal);
         }
       }
@@ -393,7 +393,7 @@ export class QuestionCheckboxModel extends QuestionCheckboxBase {
     var newValue = [];
     for (var i = 0; i < val.length; i++) {
       const rItemVal = this.getRealValue(val[i]);
-      var isUnkown = this.canClearValueAnUnknow(rItemVal);
+      var isUnkown = this.canClearValueAnUnknown(rItemVal);
       if (
         (!clearDisabled && !isUnkown) ||
         (clearDisabled && !this.isValueDisabled(rItemVal))
diff --git a/tests/question_baseselecttests.ts b/tests/question_baseselecttests.ts
index c831913822..528e8b5e51 100644
--- a/tests/question_baseselecttests.ts
+++ b/tests/question_baseselecttests.ts
@@ -987,6 +987,20 @@ QUnit.test("Carry Forward and localization, bug#6352", function (assert) {
   assert.equal(q2.visibleChoices[0].text, "A en");
   surveyLocalization.defaultLocale = "en";
 });
+QUnit.test("Carry Forward and keepIncorrectValues, bug#6490", function (assert) {
+  const survey = new SurveyModel({ elements: [
+    { type: "dropdown", name: "q1", choices: ["A", "B", "C", "D"] },
+    { type: "dropdown", name: "q2", choicesFromQuestion: "q1" }
+  ] });
+  survey.keepIncorrectValues = true;
+  survey.data = { q1: "A", q2: "X" };
+  const q1 = survey.getQuestionByName("q1");
+  const q2 = <QuestionSelectBase>survey.getQuestionByName("q2");
+  q1.value = "B";
+  assert.equal(q2.value, "X", "keep value");
+  survey.doComplete();
+  assert.deepEqual(survey.data, { q1: "B", q2: "X" }, "keep value on compete");
+});
 QUnit.test("Do not notify survey on changing newItem.value", function (
   assert
 ) {