diff --git a/lib/blockchain.py b/lib/blockchain.py
index fe599fb5..679270af 100644
--- a/lib/blockchain.py
+++ b/lib/blockchain.py
@@ -383,7 +383,8 @@ class Blockchain(util.PrintError):
     def bits_to_target(self, bits):
         bitsN = (bits >> 24) & 0xff
         if not (bitsN >= 0x03 and bitsN <= 0x1f):
-            raise Exception("First part of bits should be in [0x03, 0x1f]")
+            if not constants.net.TESTNET:
+                raise Exception("First part of bits should be in [0x03, 0x1f]")
         bitsBase = bits & 0xffffff
         if not (bitsBase >= 0x8000 and bitsBase <= 0x7fffff):
             raise Exception("Second part of bits should be in [0x8000, 0x7fffff]")