diff --git a/packages/frontend/src/components/MkImageEffectorDialog.vue b/packages/frontend/src/components/MkImageEffectorDialog.vue
index 997dd4d528..42502ba449 100644
--- a/packages/frontend/src/components/MkImageEffectorDialog.vue
+++ b/packages/frontend/src/components/MkImageEffectorDialog.vue
@@ -77,6 +77,7 @@ const dialog = useTemplateRef('dialog');
 async function cancel() {
 	if (layers.length > 0) {
 		const { canceled } = await os.confirm({
+			type: 'warning',
 			text: i18n.ts._imageEffector.discardChangesConfirm,
 		});
 		if (canceled) return;
@@ -132,7 +133,7 @@ function onLayerDelete(layer: ImageEffectorLayer) {
 
 const canvasEl = useTemplateRef('canvasEl');
 
-let renderer: ImageEffector | null = null;
+let renderer: ImageEffector<typeof FXS> | null = null;
 let imageBitmap: ImageBitmap | null = null;
 
 onMounted(async () => {
diff --git a/packages/frontend/src/components/MkWatermarkEditorDialog.Layer.vue b/packages/frontend/src/components/MkWatermarkEditorDialog.Layer.vue
index 6c81d68f85..11ae091d90 100644
--- a/packages/frontend/src/components/MkWatermarkEditorDialog.Layer.vue
+++ b/packages/frontend/src/components/MkWatermarkEditorDialog.Layer.vue
@@ -263,6 +263,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <script setup lang="ts">
 import { ref, onMounted } from 'vue';
+import * as Misskey from 'misskey-js';
 import type { WatermarkPreset } from '@/utility/watermark.js';
 import { i18n } from '@/i18n.js';
 import MkButton from '@/components/MkButton.vue';
@@ -277,7 +278,7 @@ import { misskeyApi } from '@/utility/misskey-api.js';
 
 const layer = defineModel<WatermarkPreset['layers'][number]>('layer', { required: true });
 
-const driveFile = ref();
+const driveFile = ref<Misskey.entities.DriveFile | null>(null);
 const driveFileError = ref(false);
 onMounted(async () => {
 	if (layer.value.type === 'image' && layer.value.imageId != null) {
@@ -300,6 +301,7 @@ function chooseFile(ev: MouseEvent) {
 			watermark: false,
 		},
 	}).then((file) => {
+		if (layer.value.type !== 'image') return;
 		if (!file.type.startsWith('image')) {
 			os.alert({
 				type: 'warning',
diff --git a/packages/frontend/src/utility/image-effector/ImageEffector.ts b/packages/frontend/src/utility/image-effector/ImageEffector.ts
index fe253017e5..472d21bb1b 100644
--- a/packages/frontend/src/utility/image-effector/ImageEffector.ts
+++ b/packages/frontend/src/utility/image-effector/ImageEffector.ts
@@ -57,7 +57,7 @@ function getValue<T extends keyof ParamTypeToPrimitive>(params: Record<string, a
 	return params[k];
 }
 
-export class ImageEffector {
+export class ImageEffector<IEX extends ReadonlyArray<ImageEffectorFx<any, any, any>>> {
 	private gl: WebGL2RenderingContext;
 	private canvas: HTMLCanvasElement | null = null;
 	private renderTextureProgram: WebGLProgram;
@@ -70,7 +70,7 @@ export class ImageEffector {
 	private shaderCache: Map<string, WebGLProgram> = new Map();
 	private perLayerResultTextures: Map<string, WebGLTexture> = new Map();
 	private perLayerResultFrameBuffers: Map<string, WebGLFramebuffer> = new Map();
-	private fxs: ImageEffectorFx[];
+	private fxs: [...IEX];
 	private paramTextures: Map<string, { texture: WebGLTexture; width: number; height: number; }> = new Map();
 
 	constructor(options: {
@@ -78,7 +78,7 @@ export class ImageEffector {
 		renderWidth: number;
 		renderHeight: number;
 		image: ImageData | ImageBitmap | HTMLImageElement | HTMLCanvasElement;
-		fxs: ImageEffectorFx[];
+		fxs: [...IEX];
 	}) {
 		this.canvas = options.canvas;
 		this.renderWidth = options.renderWidth;
diff --git a/packages/frontend/src/utility/image-effector/fxs.ts b/packages/frontend/src/utility/image-effector/fxs.ts
index 5887a68c43..f391314abf 100644
--- a/packages/frontend/src/utility/image-effector/fxs.ts
+++ b/packages/frontend/src/utility/image-effector/fxs.ts
@@ -35,3 +35,10 @@ export const FXS = [
 	FX_polkadot,
 	FX_checker,
 ] as const satisfies ImageEffectorFx<string, any>[];
+
+export const WATERMARK_FXS = [
+	FX_watermarkPlacement,
+	FX_stripe,
+	FX_polkadot,
+	FX_checker,
+] as const satisfies ImageEffectorFx<string, any>[];
diff --git a/packages/frontend/src/utility/watermark.ts b/packages/frontend/src/utility/watermark.ts
index 8ee93181a6..a70e14d95d 100644
--- a/packages/frontend/src/utility/watermark.ts
+++ b/packages/frontend/src/utility/watermark.ts
@@ -3,10 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import { FX_watermarkPlacement } from './image-effector/fxs/watermarkPlacement.js';
-import { FX_stripe } from './image-effector/fxs/stripe.js';
-import { FX_polkadot } from './image-effector/fxs/polkadot.js';
-import { FX_checker } from './image-effector/fxs/checker.js';
+import { WATERMARK_FXS } from './image-effector/fxs.js';
 import type { ImageEffectorLayer } from '@/utility/image-effector/ImageEffector.js';
 import { ImageEffector } from '@/utility/image-effector/ImageEffector.js';
 
@@ -64,7 +61,7 @@ export type WatermarkPreset = {
 };
 
 export class WatermarkRenderer {
-	private effector: ImageEffector;
+	private effector: ImageEffector<typeof WATERMARK_FXS>;
 	private layers: WatermarkPreset['layers'] = [];
 
 	constructor(options: {
@@ -78,7 +75,7 @@ export class WatermarkRenderer {
 			renderWidth: options.renderWidth,
 			renderHeight: options.renderHeight,
 			image: options.image,
-			fxs: [FX_watermarkPlacement, FX_stripe, FX_polkadot, FX_checker],
+			fxs: WATERMARK_FXS,
 		});
 	}
 
@@ -157,6 +154,8 @@ export class WatermarkRenderer {
 						opacity: layer.opacity,
 					},
 				};
+			} else {
+				throw new Error(`Unknown layer type`);
 			}
 		});
 	}