diff --git a/packages/deck.gl-geotiff/src/mosaic-layer/mosaic-tileset-2d.ts b/packages/deck.gl-geotiff/src/mosaic-layer/mosaic-tileset-2d.ts
index 043e40de..948921cb 100644
--- a/packages/deck.gl-geotiff/src/mosaic-layer/mosaic-tileset-2d.ts
+++ b/packages/deck.gl-geotiff/src/mosaic-layer/mosaic-tileset-2d.ts
@@ -84,6 +84,24 @@ export class MosaicTileset2D<ItemT extends MosaicItem> extends Tileset2D {
     this.getItems = getItems;
   }
 
+  /**
+   * Unloads every cached item, which deck.gl's `finalize` skips until
+   * https://github.com/visgl/deck.gl/pull/10883 lands. An item still opening
+   * is unloaded once its open finishes.
+   */
+  override finalize(): void {
+    const { onTileUnload } = this.opts;
+    for (const tile of this.tiles) {
+      if (tile.isLoading) {
+        // `data` is a promise until the load finishes
+        void Promise.resolve(tile.data).then(() => onTileUnload(tile));
+      } else {
+        onTileUnload(tile);
+      }
+    }
+    super.finalize();
+  }
+
   /** The Tileset2D cache key for an item. */
   override getTileId(tileIndex: TileIndex): string {
     // `getTileIndices` always returns `ResolvedItem`s, so an `id` is
diff --git a/packages/deck.gl-geotiff/tests/mosaic-layer.test.ts b/packages/deck.gl-geotiff/tests/mosaic-layer.test.ts
index 4b89fcd7..fa741137 100644
--- a/packages/deck.gl-geotiff/tests/mosaic-layer.test.ts
+++ b/packages/deck.gl-geotiff/tests/mosaic-layer.test.ts
@@ -248,7 +248,14 @@ function makeMosaicRenderer(viewport: WebMercatorViewport = VIEWPORT) {
     layerManager.activateViewport(next);
   };
 
-  return { render, wait, moveTo };
+  /** Remove the layer, as an app does by no longer rendering it. */
+  const remove = async () => {
+    layerManager.setLayers([]);
+    await settle(layerManager);
+    return report();
+  };
+
+  return { render, wait, moveTo, remove };
 }
 
 // The tests above reuse one layer instance. Apps create a new MosaicLayer on
@@ -455,6 +462,36 @@ describe("MosaicLayer sources", () => {
     expect(errors).toEqual([]);
     expect(unloaded).toEqual({ A: { of: "A" }, B: { of: "B" } });
   });
+
+  it("passes every cached item's source to onSourceUnload when the layer is removed", async () => {
+    const { render, remove } = makeMosaicRenderer();
+    await render({ data: [A, B] });
+
+    const { unloaded, errors } = await remove();
+    expect(errors).toEqual([]);
+    expect(unloaded).toEqual({ A: { of: "A" }, B: { of: "B" } });
+  });
+
+  it("passes the source of an item still opening at removal to onSourceUnload once it arrives", async () => {
+    const { render, remove, wait } = makeMosaicRenderer();
+    let finish!: () => void;
+    await render({
+      data: [A],
+      // Ignores the abort, as a source cache shared between loads can
+      getSource: (item) =>
+        new Promise((resolve) => {
+          finish = () => resolve({ of: item.id });
+        }),
+    });
+
+    // A copy: the report's records keep filling in
+    const atRemoval = { ...(await remove()).unloaded };
+    finish();
+    const { unloaded, errors } = await wait();
+    expect(errors).toEqual([]);
+    expect(atRemoval).toEqual({});
+    expect(unloaded).toEqual({ A: { of: "A" } });
+  });
 });
 
 describe("MosaicLayer fetch priority", () => {
diff --git a/packages/deck.gl-raster/src/raster-tileset/raster-tileset-2d.ts b/packages/deck.gl-raster/src/raster-tileset/raster-tileset-2d.ts
index aad3daa9..226fb908 100644
--- a/packages/deck.gl-raster/src/raster-tileset/raster-tileset-2d.ts
+++ b/packages/deck.gl-raster/src/raster-tileset/raster-tileset-2d.ts
@@ -263,7 +263,8 @@ export class RasterTileset2D extends Tileset2D {
    * without calling `onTileUnload`, so GPU resources that `getTileData` made
    * for those tiles, like textures, would be freed only by garbage collection.
    * A tile still loading is unloaded once its load finishes, since deck.gl
-   * keeps the data that `getTileData` returns after an abort.
+   * keeps the data that `getTileData` returns after an abort. Not needed once
+   * https://github.com/visgl/deck.gl/pull/10883 lands.
    */
   override finalize(): void {
     const { onTileUnload } = this.opts;