diff --git a/packages/core/src/visual-editing/toolbar.ts b/packages/core/src/visual-editing/toolbar.ts
index ddc6075..30a284b 100644
--- a/packages/core/src/visual-editing/toolbar.ts
+++ b/packages/core/src/visual-editing/toolbar.ts
@@ -721,6 +721,11 @@ export function renderToolbar(config: ToolbarConfig): string {
       } else {
         setSaveState("error");
         console.error("Save failed:", res.status);
+        // Reject the promise so callers know save failed
+        return res.json().then(function(e) {
+          var msg = (e && e.error && e.error.message) ? e.error.message : ("Save failed: " + res.status);
+          throw new Error(msg);
+        });
       }
     })
     .catch(function(err) {