diff --git a/lib/blockchain.py b/lib/blockchain.py
index cf516069a..7ec9aa8af 100644
--- a/lib/blockchain.py
+++ b/lib/blockchain.py
@@ -317,6 +317,8 @@ class Blockchain(util.PrintError):
         return bitsN << 24 | bitsBase
 
     def can_connect(self, header, check_height=True):
+        if header is None:
+            return False
         height = header['block_height']
         if check_height and self.height() != height - 1:
             #self.print_error("cannot connect at height", height)