diff --git a/src/common/ecs/compiler.ts b/src/common/ecs/compiler.ts
index b2220f0b..4f74380f 100644
--- a/src/common/ecs/compiler.ts
+++ b/src/common/ecs/compiler.ts
@@ -60,8 +60,14 @@ export class ECSCompiler extends Tokenizer {
         if (!this.em.imported[path]) { // already imported?
             let text = this.getImportFile && this.getImportFile(path);
             if (!text) this.compileError(`I can't find the import file "${path}".`);
-            new ECSCompiler(this.em).parseFile(path, text);
             this.em.imported[path] = true;
+            let comp = new ECSCompiler(this.em);
+            try {
+                comp.parseFile(text, path);
+            } catch (e) {
+                for (e of comp.errors) this.errors.push(e);
+                throw e;
+            }
         }
     }
 
@@ -390,6 +396,8 @@ export class ECSCompiler extends Tokenizer {
     export() {
         let src = new SourceFileExport();
         src.debug_file(this.path);
+        for (let path of Object.keys(this.em.imported))
+            src.debug_file(path);
         this.exportToFile(src);
         return src.toString();
     }
diff --git a/src/common/ecs/ecs.ts b/src/common/ecs/ecs.ts
index a5d1519e..f3ac0c21 100644
--- a/src/common/ecs/ecs.ts
+++ b/src/common/ecs/ecs.ts
@@ -1138,13 +1138,16 @@ export class EntityManager {
     constructor(public readonly dialect: Dialect_CA65) {
     }
     newScope(name: string, parent?: EntityScope) {
+        let existing = this.topScopes[name];
+        if (existing && !existing.isDemo)
+            throw new ECSError(`scope ${name} already defined`, existing);
         let scope = new EntityScope(this, this.dialect, name, parent);
-        if (this.topScopes[name]) throw new ECSError(`scope ${name} already defined`);
         if (!parent) this.topScopes[name] = scope;
         return scope;
     }
     defineComponent(ctype: ComponentType) {
-        if (this.components[ctype.name]) throw new ECSError(`component ${ctype.name} already defined`);
+        let existing = this.components[ctype.name];
+        if (existing) throw new ECSError(`component ${ctype.name} already defined`, existing);
         for (let field of ctype.fields) {
             let list = this.name2cfpairs[field.name];
             if (!list) list = this.name2cfpairs[field.name] = [];
@@ -1153,7 +1156,8 @@ export class EntityManager {
         return this.components[ctype.name] = ctype;
     }
     defineSystem(system: System) {
-        if (this.systems[system.name]) throw new ECSError(`system ${system.name} already defined`);
+        let existing = this.systems[system.name];
+        if (existing) throw new ECSError(`system ${system.name} already defined`, existing);
         for (let a of system.actions) {
             let event = a.event;
             let list = this.event2systems[event];
diff --git a/src/common/ecs/main.ts b/src/common/ecs/main.ts
index 573505dc..20057603 100644
--- a/src/common/ecs/main.ts
+++ b/src/common/ecs/main.ts
@@ -1,10 +1,10 @@
 import { readFileSync } from "fs";
 import { ECSCompiler } from "./compiler";
-import { SourceFileExport } from "./ecs";
+import { Dialect_CA65, EntityManager, SourceFileExport } from "./ecs";
 
 class ECSMain {
 
-    compiler = new ECSCompiler();
+    compiler = new ECSCompiler(new EntityManager(new Dialect_CA65())); // TODO
 
     constructor(readonly args: string[]) {
     }