diff --git a/backtesting/backtesting.py b/backtesting/backtesting.py
index d4535f44..60bcf686 100644
--- a/backtesting/backtesting.py
+++ b/backtesting/backtesting.py
@@ -1333,7 +1333,7 @@ def _optimize_grid() -> Union[pd.Series, Tuple[pd.Series, pd.Series]]:
                                     names=next(iter(param_combos)).keys()))
 
             def _batch(seq):
-                n = np.clip(len(seq) // (os.cpu_count() or 1), 5, 300)
+                n = np.clip(int(np.ceil(len(seq) / (os.cpu_count() or 1))), 1, 300)
                 for i in range(0, len(seq), n):
                     yield seq[i:i + n]