diff --git a/pygmc/devices/gmc800.py b/pygmc/devices/gmc800.py
index 0bff571..a812ff6 100644
--- a/pygmc/devices/gmc800.py
+++ b/pygmc/devices/gmc800.py
@@ -41,3 +41,5 @@ def __init__(
         # listed as RFC1201 in https://www.gqelectronicsllc.com/GMC-800UserGuide.pdf
         # https://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=10394
         # The device uses a non-published spec.
+
+        self._flash_memory_size_bytes = 2**21  # 2 MiB
diff --git a/tests/test_gmc800.py b/tests/test_gmc800.py
index d7c1af5..88c3c2a 100644
--- a/tests/test_gmc800.py
+++ b/tests/test_gmc800.py
@@ -70,6 +70,7 @@
 
 # Use our fake/mock connection in our real device class
 mock_device = devices.DeviceSpec404(mock_connection)
+mock_gmc800 = devices.GMC800(port=None, connection=mock_connection)
 
 
 @pytest.mark.parametrize("cmd,expected", parametrize_data)
@@ -98,6 +99,10 @@ def test_reset_buffers(capfd):
     assert "reset_buffers" in out
 
 
+def test_gmc800_flash_memory_size():
+    assert mock_gmc800._flash_memory_size_bytes == 2**21
+
+
 # uSv Tests
 config_calib0 = {
     "Calibration_CPM_1": 100,