diff --git a/src/devices/Ft232H/Ft232HI2cBus.cs b/src/devices/Ft232H/Ft232HI2cBus.cs
index b8287660c70509d3902832047b6807ee5b544bbe..5511afb0f9943fbe8b92c9eca244d57f6d814e33 100644
--- a/src/devices/Ft232H/Ft232HI2cBus.cs
+++ b/src/devices/Ft232H/Ft232HI2cBus.cs
@@ -37,7 +37,7 @@ namespace Iot.Device.Ft232H
         /// <inheritdoc/>
         public override I2cDevice CreateDevice(int deviceAddress)
         {
-            if (!_usedAddresses.ContainsKey(deviceAddress))
+            if (_usedAddresses.ContainsKey(deviceAddress))
             {
                 throw new ArgumentException($"Device with address 0x{deviceAddress,0X2} is already open.", nameof(deviceAddress));
             }