diff --git a/CHANGELOG.md b/CHANGELOG.md
index b4acec657..597487121 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,12 @@
 
 ## [Unreleased]
 
+### Fixed
+- Fixed importing/replacing file when file is open in editor ([support#975]).
+
+[support#975]: https://github.com/pybricks/support/issues/975
+
+
 ## [2.2.0-beta.4] - 2023-05-16
 
 ### Added
diff --git a/src/editor/actions.ts b/src/editor/actions.ts
index 1db7854e1..497eedf2c 100644
--- a/src/editor/actions.ts
+++ b/src/editor/actions.ts
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2022 The Pybricks Authors
+// Copyright (c) 2022-2023 The Pybricks Authors
 
 import { createAction } from '../actions';
 import { UUID } from '../fileStorage';
@@ -121,3 +121,14 @@ export const editorGoto = createAction((uuid: UUID, line: number) => ({
     uuid,
     line,
 }));
+
+/**
+ * Requests to replace the value a file in the editor.
+ * @param uuid The file UUID.
+ * @param value The new value for the contents of the file.
+ */
+export const editorReplaceFile = createAction((uuid: UUID, value: string) => ({
+    type: 'editor.action.replaceFile',
+    uuid,
+    value,
+}));
diff --git a/src/editor/sagas.ts b/src/editor/sagas.ts
index 5af3827ec..52ffb39b4 100644
--- a/src/editor/sagas.ts
+++ b/src/editor/sagas.ts
@@ -3,7 +3,7 @@
 
 import type { DatabaseChangeType, IDatabaseChange } from 'dexie-observable/api';
 import * as monaco from 'monaco-editor';
-import { EventChannel, buffers, eventChannel } from 'redux-saga';
+import { EventChannel, Task, buffers, eventChannel } from 'redux-saga';
 import {
     call,
     cancelled,
@@ -62,6 +62,7 @@ import {
     editorGetValueResponse,
     editorGoto,
     editorOpenFile,
+    editorReplaceFile,
 } from './actions';
 import { EditorError } from './error';
 import { ActiveFileHistoryManager, OpenFileManager } from './lib';
@@ -92,6 +93,28 @@ function* handleModelDidChange(
     }
 }
 
+function handleReplaceFile(
+    editor: monaco.editor.ICodeEditor,
+    model: monaco.editor.ITextModel,
+    action: ReturnType<typeof editorReplaceFile>,
+) {
+    // model might not be open in editor, but it doesn't hurt to do this in the
+    // open editor
+    editor.pushUndoStop();
+    // pushEditOperations says it expects a cursorComputer, but doesn't seem to need one.
+    model.pushEditOperations(
+        [],
+        [
+            {
+                range: model.getFullModelRange(),
+                text: action.value,
+            },
+        ],
+        undefined as unknown as monaco.editor.ICursorStateComputer,
+    );
+    editor.pushUndoStop();
+}
+
 function* handleEditorOpenFile(
     editor: monaco.editor.ICodeEditor,
     openFiles: OpenFileManager,
@@ -161,6 +184,14 @@ function* handleEditorOpenFile(
             // https://github.com/redux-saga/redux-saga/issues/620#issuecomment-259161095
             yield* fork(handleModelDidChange, 1000, didChangeModelChan, model);
 
+            const replaceFileTask: Task = yield* takeEvery(
+                editorReplaceFile.when((a) => a.uuid === action.uuid),
+                handleReplaceFile,
+                editor,
+                model,
+            );
+            defer.push(() => replaceFileTask.cancel());
+
             openFiles.add(action.uuid, model, didLoad.viewState);
             defer.push(() => openFiles.remove(action.uuid));
 
diff --git a/src/explorer/sagas.ts b/src/explorer/sagas.ts
index 1da7ed89a..d1008cfbe 100644
--- a/src/explorer/sagas.ts
+++ b/src/explorer/sagas.ts
@@ -20,6 +20,7 @@ import {
     editorDidActivateFile,
     editorDidCloseFile,
     editorDidFailToActivateFile,
+    editorReplaceFile,
 } from '../editor/actions';
 import { EditorError } from '../editor/error';
 import { getPybricksMicroPythonFileTemplate } from '../editor/pybricksMicroPython';
@@ -243,17 +244,26 @@ function* importPythonFile(
         fileName = accepted.newName;
     }
 
-    yield* put(fileStorageWriteFile(fileName, sourceFileContents));
+    const existingFileInfo = existingFiles.find((x) => x.path === fileName);
+    const openFileUuids = yield* select((s: RootState) => s.editor.openFileUuids);
 
-    const { didFailToWrite } = yield* race({
-        didWrite: take(fileStorageDidWriteFile.when((a) => a.path === fileName)),
-        didFailToWrite: take(
-            fileStorageDidFailToWriteFile.when((a) => a.path === fileName),
-        ),
-    });
+    // If the file is open, modify contents in the editor so preserve undo
+    // history, otherwise write directly to storage.
+    if (existingFileInfo && openFileUuids.includes(existingFileInfo.uuid)) {
+        yield* put(editorReplaceFile(existingFileInfo.uuid, sourceFileContents));
+    } else {
+        yield* put(fileStorageWriteFile(fileName, sourceFileContents));
 
-    if (didFailToWrite) {
-        throw didFailToWrite.error;
+        const { didFailToWrite } = yield* race({
+            didWrite: take(fileStorageDidWriteFile.when((a) => a.path === fileName)),
+            didFailToWrite: take(
+                fileStorageDidFailToWriteFile.when((a) => a.path === fileName),
+            ),
+        });
+
+        if (didFailToWrite) {
+            throw didFailToWrite.error;
+        }
     }
 }