diff --git a/Lib/dis.py b/Lib/dis.py
--- a/Lib/dis.py
+++ b/Lib/dis.py
@@ -370,22 +370,26 @@ def findlabels(code):
     Return the list of offsets.
 
     """
     labels = []
     # enumerate() is not an option, since we sometimes process
     # multiple elements on a single pass through the loop
     n = len(code)
     i = 0
+    extended_arg = 0
     while i < n:
         op = code[i]
         i = i+1
         if op >= HAVE_ARGUMENT:
-            arg = code[i] + code[i+1]*256
+            arg = code[i] + code[i+1]*256 + extended_arg
+            extended_arg = 0
             i = i+2
+            if op == EXTENDED_ARG:
+                extended_arg = arg*65536
             label = -1
             if op in hasjrel:
                 label = i+arg
             elif op in hasjabs:
                 label = arg
             if label >= 0:
                 if label not in labels:
                     labels.append(label)