diff --git a/src/runtime/SrcDocIFrameController.ts b/src/runtime/SrcDocIFrameController.ts
index b762527..b42dd7e 100644
--- a/src/runtime/SrcDocIFrameController.ts
+++ b/src/runtime/SrcDocIFrameController.ts
@@ -79,7 +79,9 @@ export class SrcDocIFrameController extends Disposable implements IEmbeddedConte
 
         this.addAnchorLinkHandlers();
         this.handleHashChange();
-        this.config.onload?.(this.host);
+        if (this.config.onload) {
+            this.dispose.add(() => this.config.onload?.(this.host));
+        }
     }
 
     // finds all relative links (href^="#") and changes their click behavior
diff --git a/src/types.ts b/src/types.ts
index 120ea04..084afff 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -9,7 +9,7 @@ export interface EmbedsConfig {
     classNames?: string[];
     styles?: Record<string, string>;
     isolatedSandboxHostURIOverride?: string;
-    onload?: (host: HTMLIFrameElement) => void;
+    onload?: (host: HTMLIFrameElement) => (() => void) | void;
 }
 
 export type Unsubscribe = () => void;