diff --git a/src/octoprint/util/comm.py b/src/octoprint/util/comm.py
index d0e1cd89..6dca6f01 100644
--- a/src/octoprint/util/comm.py
+++ b/src/octoprint/util/comm.py
@@ -1104,6 +1104,8 @@ class MachineCom(object):
 				self._serial.close()
 				self._serial.parity = serial.PARITY_NONE
 				self._serial.open()
+				if self._grbl :
+					self._serial.setDTR(False) # Drop DTR
 			except:
 				self._log("Unexpected error while connecting to serial port: %s %s" % (self._port, getExceptionString()))
 				self._errorValue = "Failed to open serial port, permissions correct?"