diff --git a/AMSS_NCKU_source/Parallel.C b/AMSS_NCKU_source/Parallel.C
index a0a7434..7dc3a34 100644
--- a/AMSS_NCKU_source/Parallel.C
+++ b/AMSS_NCKU_source/Parallel.C
@@ -335,7 +335,7 @@ bool cuda_can_direct_pack(const Parallel::gridseg *src, const Parallel::gridseg
     if (z4c_amr_device < 0)
     {
       const char *env = getenv("AMSS_CUDA_Z4C_AMR_DEVICE");
-      z4c_amr_device = (!env || atoi(env) != 0) ? 1 : 0;
+      z4c_amr_device = (env && atoi(env) != 0) ? 1 : 0;
     }
     if (!z4c_amr_device)
       return false;
diff --git a/makefile_and_run.py b/makefile_and_run.py
index 98114c7..7a86028 100755
--- a/makefile_and_run.py
+++ b/makefile_and_run.py
@@ -147,7 +147,7 @@ def _gpu_runtime_env():
         "AMSS_CUDA_KEEP_RESIDENT_AFTER_STEP": "1",
         "AMSS_CUDA_Z4C_KEEP_RESIDENT_AFTER_STEP": "1",
         "AMSS_CUDA_KEEP_ALL_LEVELS": "1",
-        "AMSS_CUDA_Z4C_AMR_DEVICE": "1",
+        "AMSS_CUDA_Z4C_AMR_DEVICE": "0",
         "AMSS_CUDA_AMR_RESTRICT_DEVICE": "1",
         "AMSS_CUDA_AMR_RESTRICT_BATCH": "0",
         "AMSS_CUDA_DEVICE_SEGMENT_BATCH": "0",