diff --git a/reporting/markslider.py b/reporting/markslider.py
index c4a7007..c71b032 100755
--- a/reporting/markslider.py
+++ b/reporting/markslider.py
@@ -100,6 +100,8 @@ class slide_reader:
                 self.data.append(new_page)
             f.close()
             self.file_start_page.append(len(self.data))
+        if len(self.data)==0:
+            raise ValueError("File does not have a # header")
         self.toc()
         self.pages=len(self.data)
         self.inc_page_no(0)