diff --git a/mpi_util.py b/mpi_util.py
index 7da01dc..d6a6ab7 100644
--- a/mpi_util.py
+++ b/mpi_util.py
@@ -46,7 +46,7 @@ def guess_available_gpus(n_gpus=None):
         cuda_visible_divices = os.environ['CUDA_VISIBLE_DEVICES']
         cuda_visible_divices = cuda_visible_divices.split(',')
         return [int(n) for n in cuda_visible_divices]
-    if 'RCALL_NUM_GPU' not in os.environ:
+    if 'RCALL_NUM_GPU' in os.environ:
         n_gpus = int(os.environ['RCALL_NUM_GPU'])
         return list(range(n_gpus))
     nvidia_dir = '/proc/driver/nvidia/gpus/'