diff --git a/src/rail/cli/scripts.py b/src/rail/cli/scripts.py
index fa62cff7..41c536a4 100644
--- a/src/rail/cli/scripts.py
+++ b/src/rail/cli/scripts.py
@@ -39,13 +39,14 @@ def render_nb(outdir, clear_output, dry_run, inputs, **kwargs):
             render = os.system(comline)
         status[nb_file] = render
 
-    ret_val = 0
+    failed_notebooks = []
     for key, val in status.items():
         print(f"{key} {val}")
         if val != 0:
-            ret_val = val
+            failed_notebooks.append(key)
 
-    return ret_val
+    if failed_notebooks:
+        raise ValueError(f"The following notebooks failed {str(failed_notebooks)}")
         
 
 def clone_source(outdir, git_mode, dry_run, package_file):