diff --git a/cuda_core/cuda/core/system/_field_values.pxi b/cuda_core/cuda/core/system/_field_values.pxi
index 4a9e5cc748f..d109bc2bc13 100644
--- a/cuda_core/cuda/core/system/_field_values.pxi
+++ b/cuda_core/cuda/core/system/_field_values.pxi
@@ -75,7 +75,7 @@ cdef class FieldValue:
         elif value_type == ValueType.UNSIGNED_LONG_LONG:
             return int(value.ull_val[0])
         elif value_type == ValueType.SIGNED_LONG_LONG:
-            return int(value.ll_val[0])
+            return int(value.sll_val[0])
         elif value_type == ValueType.SIGNED_INT:
             return int(value.si_val[0])
         elif value_type == ValueType.UNSIGNED_SHORT:
diff --git a/cuda_core/tests/system/test_system_device.py b/cuda_core/tests/system/test_system_device.py
index 078ca5a835c..0d55afd6f29 100644
--- a/cuda_core/tests/system/test_system_device.py
+++ b/cuda_core/tests/system/test_system_device.py
@@ -445,6 +445,19 @@ def test_field_values(subtests):
             assert field_values[0].value <= old_value
 
 
+@pytest.mark.agent_authored(model="gpt-5.6-sol")
+def test_field_value_decodes_signed_long_long():
+    """SIGNED_LONG_LONG decodes from nvmlValue_t.sll_val as a Python int."""
+    field_value = nvml.FieldValue()
+    field_value.nvml_return = int(nvml.Return.SUCCESS)
+    field_value.value_type = int(nvml.ValueType.SIGNED_LONG_LONG)
+    field_value.value.sll_val[0] = -45
+
+    value = _device.FieldValue(field_value).value
+    assert value == -45
+    assert type(value) is int
+
+
 @pytest.mark.skipif(helpers.IS_WSL or helpers.IS_WINDOWS, reason="Device attributes not supported on WSL or Windows")
 def test_get_all_devices_with_cpu_affinity(subtests):
     for i in range(multiprocessing.cpu_count()):