diff --git a/RELEASE-NOTES-1.36 b/RELEASE-NOTES-1.36
index 68a389de623..c2a6cdec5a8 100644
--- a/RELEASE-NOTES-1.36
+++ b/RELEASE-NOTES-1.36
@@ -83,6 +83,11 @@ For notes on 1.35.x and older releases, see HISTORY.
 * …
 
 === Bug fixes in 1.36 ===
+(T190285) ApiEditPage module used to switch 'undo' and 'undoafter' parameters,
+if it founds you reversed them (based on assumption that higher revision ID
+indicates a later revision). The assumption is not always true and is hindering
+proper edit undoing in some cases, hence the logic has been removed.
+Reversing the paramaters will now lead to edit conflict or undefined behavior.
 * …
 
 === Action API changes in 1.36 ===
diff --git a/includes/api/ApiEditPage.php b/includes/api/ApiEditPage.php
index b327520d2f4..36b8a091ae7 100644
--- a/includes/api/ApiEditPage.php
+++ b/includes/api/ApiEditPage.php
@@ -213,10 +213,6 @@ class ApiEditPage extends ApiBase {
 
 		if ( $params['undo'] > 0 ) {
 			if ( $params['undoafter'] > 0 ) {
-				if ( $params['undo'] < $params['undoafter'] ) {
-					list( $params['undo'], $params['undoafter'] ) =
-						[ $params['undoafter'], $params['undo'] ];
-				}
 				$undoafterRev = $revisionLookup->getRevisionById( $params['undoafter'] );
 			}
 			$undoRev = $revisionLookup->getRevisionById( $params['undo'] );
diff --git a/tests/phpunit/includes/api/ApiEditPageTest.php b/tests/phpunit/includes/api/ApiEditPageTest.php
index 72f740e73aa..fd149f2a187 100644
--- a/tests/phpunit/includes/api/ApiEditPageTest.php
+++ b/tests/phpunit/includes/api/ApiEditPageTest.php
@@ -782,11 +782,7 @@ class ApiEditPageTest extends ApiTestCase {
 
 		$text = ( new WikiPage( $titleObj ) )->getContent()->getText();
 
-		// This is wrong!  It should be 1.  But let's test for our incorrect
-		// behavior for now, so if someone fixes it they'll fix the test as
-		// well to expect 1.  If we disabled the test, it might stay disabled
-		// even once the bug is fixed, which would be a shame.
-		$this->assertSame( '2', $text );
+		$this->assertSame( '1', $text );
 	}
 
 	public function testUndoWithConflicts() {
@@ -814,10 +810,6 @@ class ApiEditPageTest extends ApiTestCase {
 		$this->assertSame( '3', $text );
 	}
 
-	/**
-	 * undoafter is supposed to be less than undo.  If not, we reverse their
-	 * meaning, so that the two are effectively interchangeable.
-	 */
 	public function testReversedUndoAfter() {
 		$name = 'Help:' . ucfirst( __FUNCTION__ );
 
@@ -834,7 +826,7 @@ class ApiEditPageTest extends ApiTestCase {
 
 		$text = ( new WikiPage( Title::newFromText( $name ) ) )->getContent()
 			->getText();
-		$this->assertSame( '1', $text );
+		$this->assertSame( '2', $text );
 	}
 
 	public function testUndoToRevFromDifferentPage() {