diff --git a/klippy/gcode.py b/klippy/gcode.py
index 184f3a81..b7d737c6 100644
--- a/klippy/gcode.py
+++ b/klippy/gcode.py
@@ -389,18 +389,24 @@ class GCodeParser:
             eventtime = self.reactor.pause(eventtime + 1.)
     def set_temp(self, params, is_bed=False, wait=False):
         temp = self.get_float('S', params, 0.)
+        heater = None
         if is_bed:
-            heater_name = 'heater_bed'
-        else:
-            index = self.get_int('T', params, 0, minval=0)
-            heater_name = 'extruder%d' % (index,)
+            heater = self.printer.lookup_object('heater_bed', None)
+        elif 'T' in params:
+            index = self.get_int('T', params, minval=0)
+            extruder = self.printer.lookup_object('extruder%d' % (index,), None)
+            if extruder is not None:
+                heater = extruder.get_heater()
+        elif self.extruder is not None:
+            heater = self.extruder.get_heater()
+        if heater is None:
+            if temp > 0.:
+                self.respond_error("Heater not configured")
+            return
         print_time = self.toolhead.get_last_move_time()
         try:
-            heater = self.heaters.lookup_heater(heater_name)
             heater.set_temp(print_time, temp)
         except heater.error as e:
-            if not temp:
-                return
             raise error(str(e))
         if wait and temp:
             self.bg_temp(heater)