diff --git a/mllam_data_prep/cli.py b/mllam_data_prep/cli.py
index 7c356c1..43dd26d 100644
--- a/mllam_data_prep/cli.py
+++ b/mllam_data_prep/cli.py
@@ -1,4 +1,5 @@
 import argparse
+import math
 import os
 from pathlib import Path
 
@@ -60,8 +61,9 @@ def call(args=None):
             )
         # get the number of system cores
         n_system_cores = os.cpu_count()
-        # compute the number of cores to use
-        n_local_cores = int(args.dask_distributed_local_core_fraction * n_system_cores)
+        # compute the number of cores to use, using ceil to ensure at least 1
+        # worker is used even on single-core machines (e.g. standard GitHub CI)
+        n_local_cores = math.ceil(args.dask_distributed_local_core_fraction * n_system_cores)
         # get the total system memory
         total_memory = psutil.virtual_memory().total
         # compute the memory per worker
diff --git a/tests/test_distributed.py b/tests/test_distributed.py
index 727f871..bdecdfa 100644
--- a/tests/test_distributed.py
+++ b/tests/test_distributed.py
@@ -28,6 +28,7 @@ def distributed():
     "args",
     [
         ["example.danra.yaml", "--dask-distributed-local-core-fraction", "1.0"],
+        ["example.danra.yaml", "--dask-distributed-local-core-fraction", "0.5"],
         ["example.danra.yaml", "--dask-distributed-local-core-fraction", "0.0"],
         ["example.danra.yaml"],
     ],