diff --git a/src/common/baseplatform.ts b/src/common/baseplatform.ts
index 763f37bc..6f6483b3 100644
--- a/src/common/baseplatform.ts
+++ b/src/common/baseplatform.ts
@@ -225,7 +225,7 @@ export abstract class BasePlatform {
   getDebugTree() : {} {
     var o : any = { };
     o.state = this.saveState();
-    if (this.debugSymbols.debuginfo) o.debuginfo = this.debugSymbols.debuginfo;
+    if (this.debugSymbols?.debuginfo) o.debuginfo = this.debugSymbols.debuginfo;
     return o;
   }
   readFile(path: string) : FileData {
diff --git a/src/platform/williams.ts b/src/platform/williams.ts
index 54de92ab..0f36acdc 100644
--- a/src/platform/williams.ts
+++ b/src/platform/williams.ts
@@ -15,7 +15,7 @@ var WilliamsPlatform = function(mainElement, proto, options) {
   var self = this;
   this.__proto__ = new (proto ? proto : Base6809Platform)();
 
-  var isDefender = options.isDefender;
+  var isDefender = options?.isDefender;
   var SCREEN_HEIGHT = 304;
   var SCREEN_WIDTH = 256;
 
@@ -303,7 +303,7 @@ var WilliamsPlatform = function(mainElement, proto, options) {
     workerchannel = new WorkerSoundChannel(worker);
     audio.master.addChannel(workerchannel);
 
-    let rotate = options.rotate == null ? -90 : parseFloat(options.rotate);
+    let rotate = options?.rotate == null ? -90 : parseFloat(options.rotate);
     video = new RasterVideo(mainElement, SCREEN_WIDTH, SCREEN_HEIGHT, { rotate });
     video.create();
     $(video.canvas).click(function(e) {
diff --git a/src/worker/tools/cc65.ts b/src/worker/tools/cc65.ts
index fe324a58..a7bebcf6 100644
--- a/src/worker/tools/cc65.ts
+++ b/src/worker/tools/cc65.ts
@@ -230,11 +230,12 @@ export function linkLD65(step: BuildStep): BuildStepResult {
             if (fn.endsWith('.lst')) {
                 var lstout = FS.readFile(fn, { encoding: 'utf8' });
                 lstout = lstout.split('\n\n')[1] || lstout; // remove header
-                var asmlines = []; // TODO: parseCA65Listing(lstout, symbolmap, params, false);
-                var srclines = parseCA65Listing(lstout, symbolmap, params, true, listings);
+                var asmlines = parseCA65Listing(lstout, symbolmap, params, false);
+                var srclines = parseCA65Listing(lstout, symbolmap, params, true); // TODO: listings param for ecs
                 putWorkFile(fn, lstout);
                 listings[fn] = {
-                    lines: [],
+                    asmlines: srclines.length ? asmlines : null,
+                    lines: srclines.length ? srclines : asmlines,
                     text: lstout
                 };
             }
diff --git a/test/cli/testplatforms.js b/test/cli/testplatforms.js
index 8889f072..64e336f9 100644
--- a/test/cli/testplatforms.js
+++ b/test/cli/testplatforms.js
@@ -196,9 +196,9 @@ async function testPlatform(platid, romname, maxframes, callback) {
       assert.equal(clks, proberec.countClocks());
     }
     // debug tree
-    if (platform.getDebugTree) {
+    if (platform.getDebugTree != null) {
       var dbgtree = platform.getDebugTree();
-      JSON.stringify(dbgtree);
+      if (dbgtree != null) JSON.stringify(dbgtree);
     }
     // misc
     assert.ok(platform.getDefaultExtension().startsWith('.'));