diff --git a/src/py65/assembler.py b/src/py65/assembler.py
index 351f10d..fd990bc 100644
--- a/src/py65/assembler.py
+++ b/src/py65/assembler.py
@@ -87,8 +87,7 @@ class Assembler:
                     # relative branch
                     absolute = int(''.join(operands), 16)
                     relative = (absolute - pc) - 2
-                    if (relative < 1): 
-                        relative = (relative ^ self.byteMask) + 1
+                    relative = relative & self.byteMask
                     operands = [ (self.byteFmt % relative) ]
 
                 elif len(operands) == 2:
diff --git a/src/py65/disassembler.py b/src/py65/disassembler.py
index bf6a5f0..749e2db 100644
--- a/src/py65/disassembler.py
+++ b/src/py65/disassembler.py
@@ -80,7 +80,7 @@ class Disassembler:
         elif addressing == 'rel':
             opv = self._mpu.ByteAt(pc + 1)
             targ = pc + 2
-            if opv & (1<<self.byteWidth):
+            if opv & (1<<(self.byteWidth-1)):
                 targ -= (opv ^ self.byteMask) + 1
             else:
                 targ += opv
diff --git a/src/py65/monitor.py b/src/py65/monitor.py
index 9febda6..a783bf4 100644
--- a/src/py65/monitor.py
+++ b/src/py65/monitor.py
@@ -236,7 +236,7 @@ class Monitor(cmd.Cmd):
             return
 
           # assemble into memory
-          bytes = self._assembler.assemble(line)
+          bytes = self._assembler.assemble(line, pc=start)
           if bytes is None:
               self.stdout.write("\r$" + (self.addrFmt % start) + "  ???\n")
               continue