diff --git a/test/functional/feature_blocksign.py b/test/functional/feature_blocksign.py
index 346dca5d8d7..7347195d64f 100755
--- a/test/functional/feature_blocksign.py
+++ b/test/functional/feature_blocksign.py
@@ -84,7 +84,7 @@ def set_test_params(self):
         self.witnessScript = signblockscript # post-dynafed this becomes witnessScript
         self.extra_args = [[
             "-signblockscript={}".format(signblockscript),
-            "-con_max_block_sig_size={}".format(self.required_signers*74),
+            "-con_max_block_sig_size={}".format(self.required_signers*74+self.num_nodes*33),
             "-anyonecanspendaremine=1",
             "-con_dyna_deploy_start=0",
         ]] * self.num_nodes