diff --git a/src/lib/types.d.ts b/src/lib/types.d.ts
index a7cbc755..e762d8b7 100644
--- a/src/lib/types.d.ts
+++ b/src/lib/types.d.ts
@@ -40,7 +40,7 @@ export interface State {
 
 export interface ValidatedState extends State {
   editorMode: EditorMode;
-  error: Error;
+  error?: Error;
   errorMarkers: MarkerData[];
   serialized: string;
 }
diff --git a/src/lib/util/state.ts b/src/lib/util/state.ts
index 6181096a..1dc7ed11 100644
--- a/src/lib/util/state.ts
+++ b/src/lib/util/state.ts
@@ -66,7 +66,7 @@ const processState = async (state: State) => {
     await parse(state.code);
     JSON.parse(state.mermaid);
   } catch (e) {
-    processed.error = e;
+    processed.error = e as Error;
     errorDebug();
     console.error(e);
     if ('hash' in e) {