diff --git a/src/PowerMeterSerialSdm.cpp b/src/PowerMeterSerialSdm.cpp
index 6901e079..42e70142 100644
--- a/src/PowerMeterSerialSdm.cpp
+++ b/src/PowerMeterSerialSdm.cpp
@@ -23,6 +23,8 @@ PowerMeterSerialSdm::~PowerMeterSerialSdm()
         _upSdmSerial->end();
         _upSdmSerial = nullptr;
     }
+
+    SerialPortManager.freePort(_sdmSerialPortOwner);
 }
 
 bool PowerMeterSerialSdm::init()