diff --git a/MicSim/components/caretaker.py b/MicSim/components/caretaker.py
index cb92cbb..b43b3e3 100644
--- a/MicSim/components/caretaker.py
+++ b/MicSim/components/caretaker.py
@@ -18,14 +18,16 @@ class Caretaker:
 			if self.objects[key] < 0:
 				return(self.objects[key])
 			elif self.objects[key]>>7==1: # If it a negative number (2 complement)
-				return(-(self.objects[key]&0x7F))
+				#return(-(self.objects[key]&0x7F)) 
+				return(-((self.objects[key]-1)^0xFF)) # Reverse 2 complements to get an unsign nummber (for python is better)
+
 			else:
 				return(self.objects[key])
 		return(self.objects[key])
 
 	def __setitem__(self,key,value):
 		if key!="RAM":
-			if (-(2**7-1))>value and (key=="MBR" or key=="MBRU"):
+			if ((-(2**7-1))>value or value>(2**8)-1) and (key=="MBR" or key=="MBRU"):
 				raise RuntimeError("Value {} cannot fit in MBR register (-2^7 minimum value)".format(value))
 			elif value>(2**32-1) and (key!="MBR" and key!="MBRU"):
 				raise RuntimeError("Value {} cannot fit in MBR register (2^32 minimum value)".format(value))
diff --git a/MicSim/test/test_caretaker.py b/MicSim/test/test_caretaker.py
index e4b8dfb..414bf37 100644
--- a/MicSim/test/test_caretaker.py
+++ b/MicSim/test/test_caretaker.py
@@ -25,7 +25,7 @@ class CaretakerTest(unittest.TestCase):
 			self.c["MBR"]=toWrite
 			self.assertEqual(self.c["MBRU"],toWrite,"Tested with {}".format(toWrite))
 			if toWrite>127: # We enter in the zone of negative number at 127
-				self.assertEqual(self.c["MBR"],-(toWrite&0x7F),"Tested with {}".format(toWrite))
+				self.assertEqual(self.c["MBR"],-((toWrite-1)^0xFF),"Tested with {}".format(toWrite)) # Check if we get the reverse complement
 
 		with self.assertRaises(KeyError): # Check it returns a KeyError
 			self.c["kjhkjhkoih"+str(randint(0,7698))]