diff --git a/src/meter_em24.cc b/src/meter_em24.cc
index ae9bd4f..55f2af3 100644
--- a/src/meter_em24.cc
+++ b/src/meter_em24.cc
@@ -39,7 +39,7 @@ constexpr uint8_t ERROR_CODE_FREQUENCY_OUT_OF_RANGE=0x40;
 
 
 struct MeterEM24 : public virtual ElectricityMeter, public virtual MeterCommonImplementation {
-    MeterEM24(WMBus *bus, MeterInfo &mi);
+    MeterEM24(MeterInfo &mi);
 
     double totalEnergyConsumption(Unit u);
     double totalEnergyProduction(Unit u);
@@ -64,13 +64,13 @@ private:
     uint8_t error_codes_ {};
 };
 
-unique_ptr<ElectricityMeter> createEM24(WMBus *bus, MeterInfo &mi)
+shared_ptr<ElectricityMeter> createEM24(MeterInfo &mi)
 {
-    return unique_ptr<ElectricityMeter>(new MeterEM24(bus, mi));
+    return shared_ptr<ElectricityMeter>(new MeterEM24(mi));
 }
 
-MeterEM24::MeterEM24(WMBus *bus, MeterInfo &mi) :
-    MeterCommonImplementation(bus, mi, MeterType::EM24)
+MeterEM24::MeterEM24(MeterInfo &mi) :
+    MeterCommonImplementation(mi, MeterType::EM24)
 {
     setExpectedELLSecurityMode(ELLSecurityMode::AES_CTR);
 
@@ -173,7 +173,7 @@ void MeterEM24::processContent(Telegram *t)
     // 75 vife (Cold / Warm Temperature Limit 10^-2 Celsius)
     extractDVdouble(&t->values, "04FB8275", &offset, &total_reactive_energy_consumption_kvarh_);
     t->addMoreExplanation(offset, " total reactive power (%f kvarh)", total_reactive_energy_consumption_kvarh_);
-    
+
     // 04 dif (32 Bit Integer/Binary Instantaneous value)
     // 85 vif (Energy 10² Wh)
     // 3C vife (backward flow)
@@ -187,7 +187,7 @@ void MeterEM24::processContent(Telegram *t)
     // 3C vife (Reserved)
     extractDVdouble(&t->values, "04FB82F53C", &offset, &total_reactive_energy_production_kvarh_);
     t->addMoreExplanation(offset, " total reactive power (%f kvarh)", total_reactive_energy_production_kvarh_);
- 
+
     // 01 dif (8 Bit Integer/Binary Instantaneous value)
     // FD vif (Second extension of VIF-codes)
     // 17 vife (Error flags (binary))
diff --git a/src/serial.cc b/src/serial.cc
index abc5d47..de821e3 100644
--- a/src/serial.cc
+++ b/src/serial.cc
@@ -149,6 +149,7 @@ struct SerialDeviceImp : public SerialDevice
     void fill(vector<uchar> &data) {};
     int receive(vector<uchar> *data);
     bool working() { return fd_ != -1; }
+    bool opened() { return fd_ != -2; }
     bool readonly() { return is_stdin_ || is_file_; }
 
     void expectAscii() { expecting_ascii_ = true; }
@@ -174,7 +175,7 @@ protected:
 
     function<void()> on_data_;
     function<void()> on_disappear_;
-    int fd_ = -1;
+    int fd_ = -2; // -2 not yet opened, -1 not working
     bool expecting_ascii_ {}; // If true, print using safeString instead if bin2hex
     bool is_file_ = false;
     bool is_stdin_ = false;
diff --git a/src/serial.h b/src/serial.h
index 7fcc2ee..6d739b9 100644
--- a/src/serial.h
+++ b/src/serial.h
@@ -44,6 +44,7 @@ struct SerialDevice
     // Receive returns the number of bytes received.
     virtual int receive(std::vector<uchar> *data) = 0;
     virtual int fd() = 0;
+    virtual bool opened() = 0;
     virtual bool working() = 0;
     // Used when connecting stdin to a tty driver for testing.
     virtual bool readonly() = 0;
diff --git a/src/wmbus.cc b/src/wmbus.cc
index 493fea6..5c1e057 100644
--- a/src/wmbus.cc
+++ b/src/wmbus.cc
@@ -3345,7 +3345,7 @@ bool WMBusCommonImplementation::reset()
     bool resetting = false;
     if (serial())
     {
-        if (serial()->working())
+        if (serial()->opened() && serial()->working())
         {
             // This is a reset, not an init. Close the serial device.
             resetting = true;