diff --git a/src/vs/workbench/common/editor/diffEditorInput.ts b/src/vs/workbench/common/editor/diffEditorInput.ts
index 61adcbef85f..57a88555f35 100644
--- a/src/vs/workbench/common/editor/diffEditorInput.ts
+++ b/src/vs/workbench/common/editor/diffEditorInput.ts
@@ -6,7 +6,7 @@
 import { AbstractSideBySideEditorInputSerializer, SideBySideEditorInput } from 'vs/workbench/common/editor/sideBySideEditorInput';
 import { EditorInput } from 'vs/workbench/common/editor/editorInput';
 import { EditorModel } from 'vs/workbench/common/editor/editorModel';
-import { TEXT_DIFF_EDITOR_ID, BINARY_DIFF_EDITOR_ID, Verbosity, IEditorDescriptor, IEditorPane, GroupIdentifier, IResourceDiffEditorInput, IEditorInput, IUntypedEditorInput, DEFAULT_EDITOR_ASSOCIATION, UntypedEditorContext } from 'vs/workbench/common/editor';
+import { TEXT_DIFF_EDITOR_ID, BINARY_DIFF_EDITOR_ID, Verbosity, IEditorDescriptor, IEditorPane, GroupIdentifier, IResourceDiffEditorInput, IEditorInput, IUntypedEditorInput, DEFAULT_EDITOR_ASSOCIATION, UntypedEditorContext, isResourceDiffEditorInput } from 'vs/workbench/common/editor';
 import { BaseTextEditorModel } from 'vs/workbench/common/editor/textEditorModel';
 import { DiffEditorModel } from 'vs/workbench/common/editor/diffEditorModel';
 import { TextDiffEditorModel } from 'vs/workbench/common/editor/textDiffEditorModel';
@@ -154,6 +154,10 @@ export class DiffEditorInput extends SideBySideEditorInput {
 	}
 
 	override matches(otherInput: IEditorInput | IUntypedEditorInput): boolean {
+		if (isResourceDiffEditorInput(otherInput)) {
+			return this.modifiedInput.matches(otherInput.modifiedInput) && this.originalInput.matches(otherInput.originalInput);
+		}
+
 		if (!super.matches(otherInput)) {
 			return false;
 		}
diff --git a/src/vs/workbench/test/browser/parts/editor/editorGroupModel.test.ts b/src/vs/workbench/test/browser/parts/editor/editorGroupModel.test.ts
index 70d4a4fb85f..7a753f2bc30 100644
--- a/src/vs/workbench/test/browser/parts/editor/editorGroupModel.test.ts
+++ b/src/vs/workbench/test/browser/parts/editor/editorGroupModel.test.ts
@@ -5,7 +5,7 @@
 
 import * as assert from 'assert';
 import { EditorGroupModel, ISerializedEditorGroupModel, EditorCloseEvent } from 'vs/workbench/common/editor/editorGroupModel';
-import { EditorExtensions, IEditorInputFactoryRegistry, IFileEditorInput, IEditorInputSerializer, CloseDirection, EditorsOrder } from 'vs/workbench/common/editor';
+import { EditorExtensions, IEditorInputFactoryRegistry, IFileEditorInput, IEditorInputSerializer, CloseDirection, EditorsOrder, IResourceDiffEditorInput } from 'vs/workbench/common/editor';
 import { URI } from 'vs/base/common/uri';
 import { TestLifecycleService, workbenchInstantiationService } from 'vs/workbench/test/browser/workbenchTestServices';
 import { TestConfigurationService } from 'vs/platform/configuration/test/common/testConfigurationService';
@@ -296,7 +296,97 @@ suite('EditorGroupModel', () => {
 		assert.ok(!group.isActive(untypedNonActiveInput));
 	});
 
-	test('contains()', function () {
+	test('contains() - untyped', function () {
+		const group = createEditorGroupModel();
+		const instantiationService = workbenchInstantiationService();
+
+		const input1 = input('input1', false, URI.file('/input1'));
+		const input2 = input('input2', false, URI.file('/input2'));
+
+		const untypedInput1 = { resource: URI.file('/input1'), options: { override: 'input1' } };
+		const untypedInput2 = { resource: URI.file('/input2'), options: { override: 'input2' } };
+
+		const diffInput1 = instantiationService.createInstance(DiffEditorInput, 'name', 'description', input1, input2, undefined);
+		const diffInput2 = instantiationService.createInstance(DiffEditorInput, 'name', 'description', input2, input1, undefined);
+
+		const untypedDiffInput1: IResourceDiffEditorInput = {
+			originalInput: untypedInput1,
+			modifiedInput: untypedInput2
+		};
+		const untypedDiffInput2: IResourceDiffEditorInput = {
+			originalInput: untypedInput2,
+			modifiedInput: untypedInput1
+		};
+
+		group.openEditor(input1, { pinned: true, active: true });
+
+		assert.strictEqual(group.contains(untypedInput1), true);
+		assert.strictEqual(group.contains(untypedInput1, { strictEquals: true }), false);
+		assert.strictEqual(group.contains(untypedInput1, { supportSideBySide: true }), true);
+		assert.strictEqual(group.contains(untypedInput2), false);
+		assert.strictEqual(group.contains(untypedInput2, { strictEquals: true }), false);
+		assert.strictEqual(group.contains(untypedInput2, { supportSideBySide: true }), false);
+		assert.strictEqual(group.contains(untypedDiffInput1), false);
+		assert.strictEqual(group.contains(untypedDiffInput2), false);
+
+		group.openEditor(input2, { pinned: true, active: true });
+
+		assert.strictEqual(group.contains(untypedInput1), true);
+		assert.strictEqual(group.contains(untypedInput2), true);
+		assert.strictEqual(group.contains(untypedDiffInput1), false);
+		assert.strictEqual(group.contains(untypedDiffInput2), false);
+
+		group.openEditor(diffInput1, { pinned: true, active: true });
+
+		assert.strictEqual(group.contains(untypedInput1), true);
+		assert.strictEqual(group.contains(untypedInput2), true);
+		assert.strictEqual(group.contains(untypedDiffInput1), true);
+		assert.strictEqual(group.contains(untypedDiffInput2), false);
+
+		group.openEditor(diffInput2, { pinned: true, active: true });
+
+		assert.strictEqual(group.contains(untypedInput1), true);
+		assert.strictEqual(group.contains(untypedInput2), true);
+		assert.strictEqual(group.contains(untypedDiffInput1), true);
+		assert.strictEqual(group.contains(untypedDiffInput2), true);
+
+		group.closeEditor(input1);
+
+		assert.strictEqual(group.contains(untypedInput1), false);
+		assert.strictEqual(group.contains(untypedInput1, { supportSideBySide: true }), true);
+		assert.strictEqual(group.contains(untypedInput2), true);
+		assert.strictEqual(group.contains(untypedDiffInput1), true);
+		assert.strictEqual(group.contains(untypedDiffInput2), true);
+
+		group.closeEditor(input2);
+
+		assert.strictEqual(group.contains(untypedInput1), false);
+		assert.strictEqual(group.contains(untypedInput1, { supportSideBySide: true }), true);
+		assert.strictEqual(group.contains(untypedInput2), false);
+		assert.strictEqual(group.contains(untypedInput2, { supportSideBySide: true }), true);
+		assert.strictEqual(group.contains(untypedDiffInput1), true);
+		assert.strictEqual(group.contains(untypedDiffInput2), true);
+
+		group.closeEditor(diffInput1);
+
+		assert.strictEqual(group.contains(untypedInput1), false);
+		assert.strictEqual(group.contains(untypedInput1, { supportSideBySide: true }), true);
+		assert.strictEqual(group.contains(untypedInput2), false);
+		assert.strictEqual(group.contains(untypedInput2, { supportSideBySide: true }), true);
+		assert.strictEqual(group.contains(untypedDiffInput1), false);
+		assert.strictEqual(group.contains(untypedDiffInput2), true);
+
+		group.closeEditor(diffInput2);
+
+		assert.strictEqual(group.contains(untypedInput1), false);
+		assert.strictEqual(group.contains(untypedInput1, { supportSideBySide: true }), false);
+		assert.strictEqual(group.contains(untypedInput2), false);
+		assert.strictEqual(group.contains(untypedInput2, { supportSideBySide: true }), false);
+		assert.strictEqual(group.contains(untypedDiffInput1), false);
+		assert.strictEqual(group.contains(untypedDiffInput2), false);
+	});
+
+	test('contains()', () => {
 		const group = createEditorGroupModel();
 		const instantiationService = workbenchInstantiationService();