diff --git a/src/common/toolmeta.ts b/src/common/toolmeta.ts
index e3de6d07..b796c22a 100644
--- a/src/common/toolmeta.ts
+++ b/src/common/toolmeta.ts
@@ -284,7 +284,7 @@ export const TOOL_META: { [id: string]: ToolMeta } = {
 
   ca65: {
     id: 'ca65', name: 'ca65', kind: 'assembler', arch: '6502',
-    extensions: ['.s', '.ca65'],
+    extensions: ['.s', '.ca65', '.inc'],
     includeDirs: ['/include', '/asminc'],
     editorStyle: '6502',
     helpURL: 'https://cc65.github.io/doc/ca65.html',
@@ -698,8 +698,16 @@ export function getPreloadFSName(tool: string, platform?: string): string | unde
   if (!meta) return undefined;
   if (meta.platforms) {
     if (platform) {
+      // Try the exact id, then the root base id so suffixed platform ids
+      // (e.g. 'atari8-800', 'atari8-5200.xlmame') resolve to the shared
+      // filesystem registered under the root ('atari8' -> '65-atari8').
       let p = meta.platforms[platform];
       if (p && p.preloadFS) return p.preloadFS;
+      let base = getRootBasePlatform(platform);
+      if (base && base !== platform) {
+        let b = meta.platforms[base];
+        if (b && b.preloadFS) return b.preloadFS;
+      }
     }
     let d = meta.platforms['default'];
     if (d && d.preloadFS) return d.preloadFS;
diff --git a/src/worker/workerlib.ts b/src/worker/workerlib.ts
index 3e27eb89..11d8203d 100644
--- a/src/worker/workerlib.ts
+++ b/src/worker/workerlib.ts
@@ -6,7 +6,6 @@
 import * as fs from 'fs';
 import * as path from 'path';
 import type { WorkerResult, WorkerMessage } from "../common/workertypes";
-import { getBasePlatform, getRootBasePlatform } from "../common/util";
 import { getPreloadFSName } from "../common/toolmeta";
 import { store, builder } from "./builder";
 import { emglobal, fsMeta, loadFilesystem, listSharedFiles, readSharedFile, ensureFilesystem, readWasiSharedFile, listWasiSharedFiles, ensureWasiFilesystem } from "./wasmutils";
@@ -136,8 +135,7 @@ export function setupNodeEnvironment() {
 export async function handleMessage(data: WorkerMessage): Promise<WorkerResult> {
   // preload file system
   if (data.preload) {
-    var fsName = getPreloadFSName(data.preload, data.platform && getBasePlatform(data.platform))
-      || getPreloadFSName(data.preload, data.platform && getRootBasePlatform(data.platform));
+    var fsName = getPreloadFSName(data.preload, data.platform);
     if (fsName && !fsMeta[fsName])
       loadFilesystem(fsName);
     return;
diff --git a/src/worker/workermain.ts b/src/worker/workermain.ts
index f28c751f..8eea144f 100644
--- a/src/worker/workermain.ts
+++ b/src/worker/workermain.ts
@@ -1,6 +1,5 @@
 
 import type { WorkerResult, WorkerMessage, WorkerError, SourceLine } from "../common/workertypes";
-import { getBasePlatform, getRootBasePlatform } from "../common/util";
 import { getPreloadFSName } from "../common/toolmeta";
 import { store, builder, errorResult, getWorkFileAsString } from "./builder";
 import { emglobal, fsMeta, loadFilesystem, listSharedFiles, readSharedFile, ensureFilesystem, readWasiSharedFile, listWasiSharedFiles, ensureWasiFilesystem } from "./wasmutils";
@@ -37,8 +36,7 @@ export function setupRequireFunction() {
 async function handleMessage(data: WorkerMessage): Promise<WorkerResult> {
   // preload file system
   if (data.preload) {
-    var fs = getPreloadFSName(data.preload, data.platform && getBasePlatform(data.platform))
-      || getPreloadFSName(data.preload, data.platform && getRootBasePlatform(data.platform));
+    var fs = getPreloadFSName(data.preload, data.platform);
     if (fs && !fsMeta[fs])
       loadFilesystem(fs);
     return;
diff --git a/test/unit/testtoolmeta.ts b/test/unit/testtoolmeta.ts
index ffb6cf98..0d1c4ce8 100644
--- a/test/unit/testtoolmeta.ts
+++ b/test/unit/testtoolmeta.ts
@@ -53,6 +53,15 @@ describe('Tool metadata registry', function () {
     assert.strictEqual(getPreloadFSName('dasm'), undefined);
   });
 
+  it('getPreloadFSName resolves suffixed platform ids to their root base', function () {
+    // atari8 runs as 'atari8-800' / 'atari8-5200' / *.xlmame variants
+    assert.strictEqual(getPreloadFSName('cc65', 'atari8'), '65-atari8');
+    assert.strictEqual(getPreloadFSName('cc65', 'atari8-800'), '65-atari8');
+    assert.strictEqual(getPreloadFSName('cc65', 'atari8-800.xlmame'), '65-atari8');
+    assert.strictEqual(getPreloadFSName('cc65', 'atari8-5200'), '65-atari8');
+    assert.strictEqual(getSharedFileSystemName('cc65', 'atari8-800'), '65-atari8');
+  });
+
   it('getSkeletonName defaults to the tool id', function () {
     assert.strictEqual(getSkeletonName('dasm'), 'dasm');
     assert.strictEqual(getSkeletonName('remote:llvm-mos'), 'llvm-mos');