diff --git a/bind/G4Calo.py b/bind/G4Calo.py
index bb808e8..fb99a49 100644
--- a/bind/G4Calo.py
+++ b/bind/G4Calo.py
@@ -188,7 +188,8 @@ def run_batch(
         minEnergy_GeV: float,
         maxEnergy_GeV: float = -1.0,
         filename: str = "",
-        no_mp: bool = False):
+        no_mp: bool = False,
+        manual_seed : int = -1):
     '''
     splits the batch in jobs depending on how many cores are available and runs mini batches in parallel
     '''
@@ -215,15 +216,18 @@ def run_batch(
     
     nevents = [nEventsPerCore if i < nCores - 1 else nEventsLastCore for i in range(nCores)]
 
-    with _g4calo_threading_lock if _g4calo_threading_lock is not None else contextlib.nullcontext():
-        # check if file exists, if so, read last seed. If not create it
-        if os.path.exists(os.path.expanduser("~/.g4calo_seeds.txt")):
-            with open(os.path.expanduser("~/.g4calo_seeds.txt"), "r") as f:
-                seed = int(f.read())
-        else:
-            seed = 0
-        with open(os.path.expanduser("~/.g4calo_seeds.txt"), "w") as f:
-            f.write(str(seed + nCores))
+    if manual_seed >= 0:
+        seed = manual_seed 
+    else:
+        with _g4calo_threading_lock if _g4calo_threading_lock is not None else contextlib.nullcontext():
+            # check if file exists, if so, read last seed. If not create it
+            if os.path.exists(os.path.expanduser("~/.g4calo_seeds.txt")):
+                with open(os.path.expanduser("~/.g4calo_seeds.txt"), "r") as f:
+                    seed = int(f.read())
+            else:
+                seed = 0
+            with open(os.path.expanduser("~/.g4calo_seeds.txt"), "w") as f:
+                f.write(str(seed + nCores))
 
     seed += 1
     print(f"Batch seed: {seed}")