diff --git a/nbval/plugin.py b/nbval/plugin.py
index ee3ff29..951141c 100644
--- a/nbval/plugin.py
+++ b/nbval/plugin.py
@@ -311,7 +311,7 @@ def collect(self):
         self.nb = nbformat.read(str(self.fspath), as_version=4)
 
         # Start the cell count
-        cell_num = 0
+        cell_num = 1
 
         # Iterate over the cells in the notebook
         for cell in self.nb.cells: