diff -r 83814cdca928 Lib/dis.py
--- a/Lib/dis.py	Sun Feb 28 21:13:44 2016 +0100
+++ b/Lib/dis.py	Sun Feb 28 12:57:16 2016 -0800
@@ -272,6 +272,23 @@
     return argval, argrepr
 
 
+def _scan_op_args(code):
+    """Iterate over code for the next op and arg, isolating EXTENDED_ARG handling."""
+    extended_arg = 0
+    next_i = 0
+    n = len(code)
+    while next_i < n:
+        this_i = next_i
+        op = code[next_i]
+        next_i += 1
+        if op < HAVE_ARGUMENT:
+            arg = None
+        else:
+            arg = code[next_i] + code[next_i+1]*256 + extended_arg*65536
+            next_i += 2
+            extended_arg = arg if op == EXTENDED_ARG else 0
+        yield this_i, next_i, op, arg
+
 def _get_instructions_bytes(code, varnames=None, names=None, constants=None,
                       cells=None, linestarts=None, line_offset=0):
     """Iterate over the instructions in a bytecode string.
@@ -283,33 +300,19 @@
 
     """
     labels = findlabels(code)
-    extended_arg = 0
     starts_line = None
-    free = None
-    # enumerate() is not an option, since we sometimes process
-    # multiple elements on a single pass through the loop
-    n = len(code)
-    i = 0
-    while i < n:
-        op = code[i]
-        offset = i
+    for i, offset, op, arg in _scan_op_args(code):
         if linestarts is not None:
             starts_line = linestarts.get(i, None)
             if starts_line is not None:
                 starts_line += line_offset
         is_jump_target = i in labels
-        i = i+1
         arg = None
         argval = None
         argrepr = ''
-        if op >= HAVE_ARGUMENT:
-            arg = code[i] + code[i+1]*256 + extended_arg
-            extended_arg = 0
-            i = i+2
-            if op == EXTENDED_ARG:
-                extended_arg = arg*65536
+        if arg is not None:
             #  Set argval to the dereferenced value of the argument when
-            #  availabe, and argrepr to the string representation of argval.
+            #  available, and argrepr to the string representation of argval.
             #    _disassemble_bytes needs the string repr of the
             #    raw name index for LOAD_GLOBAL, LOAD_CONST, etc.
             argval = arg
@@ -318,7 +321,7 @@
             elif op in hasname:
                 argval, argrepr = _get_name_info(arg, names)
             elif op in hasjrel:
-                argval = i + arg
+                argval = offset + arg
                 argrepr = "to " + repr(argval)
             elif op in haslocal:
                 argval, argrepr = _get_name_info(arg, varnames)
@@ -328,10 +331,10 @@
             elif op in hasfree:
                 argval, argrepr = _get_name_info(arg, cells)
             elif op in hasnargs:
-                argrepr = "%d positional, %d keyword pair" % (code[i-2], code[i-1])
+                argrepr = "%d positional, %d keyword pair" % (code[offset-2], code[offset-1])
         yield Instruction(opname[op], op,
                           arg, argval, argrepr,
-                          offset, starts_line, is_jump_target)
+                          i, starts_line, is_jump_target)
 
 def disassemble(co, lasti=-1, *, file=None):
     """Disassemble a code object."""
@@ -371,24 +374,15 @@
 
     """
     labels = []
-    # enumerate() is not an option, since we sometimes process
-    # multiple elements on a single pass through the loop
-    n = len(code)
-    i = 0
-    while i < n:
-        op = code[i]
-        i = i+1
-        if op >= HAVE_ARGUMENT:
-            arg = code[i] + code[i+1]*256
-            i = i+2
+    for _, offset, op, arg in _scan_op_args(code):
+        if arg is not None:
             label = -1
             if op in hasjrel:
-                label = i+arg
+                label = offset+arg
             elif op in hasjabs:
                 label = arg
-            if label >= 0:
-                if label not in labels:
-                    labels.append(label)
+            if label >= 0 and label not in labels:
+                labels.append(label)
     return labels
 
 def findlinestarts(code):