diff --git a/FirmwareUpdateWindow.qml b/FirmwareUpdateWindow.qml
index 2ae6ed40d5..e3777e853f 100644
--- a/FirmwareUpdateWindow.qml
+++ b/FirmwareUpdateWindow.qml
@@ -9,7 +9,7 @@ Rectangle
 
         Text 
         {
-            text: "Updating firmware
+            text: "Updating firmware"
         }
         ProgressBar 
         {
diff --git a/PrinterConnection.py b/PrinterConnection.py
index d5fb1e1690..d94beea6c5 100644
--- a/PrinterConnection.py
+++ b/PrinterConnection.py
@@ -117,9 +117,9 @@ class PrinterConnection(SignalEmitter):
             self._connect_thread.start()
 
     def updateFirmware(self, file_name):
+        print("Update firmware; " , self._is_connecting, " ", self._is_connected )
         if self._is_connecting or  self._is_connected:
-            return False
-
+            self.close()
         hex_file = intelHex.readHex(file_name)
         if len(hex_file) == 0:
             Logger.log('e', "Unable to read provided hex file. Could not update firmware")
@@ -136,7 +136,7 @@ class PrinterConnection(SignalEmitter):
             programmer.programChip(hex_file)
             self._updating_firmware = False
         except Exception as e:
-            Logger.log("e", "Exception while trying to update firmware" , e)
+            Logger.log("e", "Exception while trying to update firmware %s" %e)
             self._updating_firmware = False
             return False
         programmer.close()
@@ -173,6 +173,9 @@ class PrinterConnection(SignalEmitter):
             self._sendCommand("M105")  #Request temperature, as this should (if baudrate is correct) result in a command with 'T:' in it
             while timeout_time > time.time():
                 line = self._readline() 
+                if line is None:
+                    self.setIsConnected(False) # something went wrong with reading, could be that close was called.
+                    return
                 if b"T:" in line:
                     self._serial.timeout = 0.5
                     self._serial.write(b"\n")
diff --git a/avr_isp/intelHex.py b/avr_isp/intelHex.py
index 75c7d3a5b2..822936ef1b 100644
--- a/avr_isp/intelHex.py
+++ b/avr_isp/intelHex.py
@@ -34,7 +34,7 @@ def readHex(filename):
         if recType == 0:#Data record
             while len(data) < addr + recLen:
                 data.append(0)
-            for i in xrange(0, recLen):
+            for i in range(0, recLen):
                 data[addr + i] = int(line[i*2+9:i*2+11], 16)
         elif recType == 1:	#End Of File record
             pass
diff --git a/avr_isp/stk500v2.py b/avr_isp/stk500v2.py
index b2d2449727..778adc7da3 100644
--- a/avr_isp/stk500v2.py
+++ b/avr_isp/stk500v2.py
@@ -86,7 +86,7 @@ class Stk500v2(ispBase.IspBase):
             self.sendMessage([0x06, 0x00, 0x00, 0x00, 0x00])
         
         loadCount = (len(flashData) + pageSize - 1) / pageSize
-        for i in xrange(0, loadCount):
+        for i in range(0, loadCount):
             recv = self.sendMessage([0x13, pageSize >> 8, pageSize & 0xFF, 0xc1, 0x0a, 0x40, 0x4c, 0x20, 0x00, 0x00] + flashData[(i * pageSize):(i * pageSize + pageSize)])
             if self.progressCallback is not None:
                 if self._has_checksum:
@@ -114,11 +114,11 @@ class Stk500v2(ispBase.IspBase):
                 self.sendMessage([0x06, 0x00, 0x00, 0x00, 0x00])
 
             loadCount = (len(flashData) + 0xFF) / 0x100
-            for i in xrange(0, loadCount):
+            for i in range(0, loadCount):
                 recv = self.sendMessage([0x14, 0x01, 0x00, 0x20])[2:0x102]
                 if self.progressCallback is not None:
                     self.progressCallback(loadCount + i + 1, loadCount*2)
-                for j in xrange(0, 0x100):
+                for j in range(0, 0x100):
                     if i * 0x100 + j < len(flashData) and flashData[i * 0x100 + j] != recv[j]:
                         raise ispBase.IspError('Verify error at: 0x%x' % (i * 0x100 + j))