diff --git a/test/functional/feature_bip68_sequence.py b/test/functional/feature_bip68_sequence.py
index fe45ed34b5c..549e8b2029a 100755
--- a/test/functional/feature_bip68_sequence.py
+++ b/test/functional/feature_bip68_sequence.py
@@ -324,7 +324,7 @@ class BIP68Test(BitcoinTestFramework):
             block.solve()
             tip = block.sha256
             height += 1
-            self.nodes[0].submitblock(ToHex(block))
+            assert_equal(None if i == 1 else 'inconclusive', self.nodes[0].submitblock(ToHex(block)))
             cur_time += 1
 
         mempool = self.nodes[0].getrawmempool()
@@ -381,7 +381,7 @@ class BIP68Test(BitcoinTestFramework):
         add_witness_commitment(block)
         block.solve()
 
-        self.nodes[0].submitblock(block.serialize().hex())
+        assert_equal(None, self.nodes[0].submitblock(block.serialize().hex()))
         assert_equal(self.nodes[0].getbestblockhash(), block.hash)
 
     def activateCSV(self):
diff --git a/test/functional/feature_nulldummy.py b/test/functional/feature_nulldummy.py
index 12471c5088c..ff55cb76d95 100755
--- a/test/functional/feature_nulldummy.py
+++ b/test/functional/feature_nulldummy.py
@@ -111,7 +111,7 @@ class NULLDUMMYTest(BitcoinTestFramework):
         witness and add_witness_commitment(block)
         block.rehash()
         block.solve()
-        node.submitblock(block.serialize().hex())
+        assert_equal(None if accept else 'block-validation-failed', node.submitblock(block.serialize().hex()))
         if (accept):
             assert_equal(node.getbestblockhash(), block.hash)
             self.tip = block.sha256
diff --git a/test/functional/p2p_segwit.py b/test/functional/p2p_segwit.py
index 09089371d37..25e2f39c6a6 100755
--- a/test/functional/p2p_segwit.py
+++ b/test/functional/p2p_segwit.py
@@ -862,13 +862,13 @@ class SegWitTest(BitcoinTestFramework):
 
         # We can't send over the p2p network, because this is too big to relay
         # TODO: repeat this test with a block that can be relayed
-        self.nodes[0].submitblock(block.serialize().hex())
+        assert_equal('bad-witness-nonce-size', self.nodes[0].submitblock(block.serialize().hex()))
 
         assert self.nodes[0].getbestblockhash() != block.hash
 
         block.vtx[0].wit.vtxinwit[0].scriptWitness.stack.pop()
         assert get_virtual_size(block) < MAX_BLOCK_BASE_SIZE
-        self.nodes[0].submitblock(block.serialize().hex())
+        assert_equal(None, self.nodes[0].submitblock(block.serialize().hex()))
 
         assert self.nodes[0].getbestblockhash() == block.hash
 
@@ -975,14 +975,14 @@ class SegWitTest(BitcoinTestFramework):
         add_witness_commitment(block, nonce=1)
         block.vtx[0].wit = CTxWitness()  # drop the nonce
         block.solve()
-        self.nodes[0].submitblock(block.serialize().hex())
+        assert_equal('bad-witness-merkle-match', self.nodes[0].submitblock(block.serialize().hex()))
         assert self.nodes[0].getbestblockhash() != block.hash
 
         # Now redo commitment with the standard nonce, but let bitcoind fill it in.
         add_witness_commitment(block, nonce=0)
         block.vtx[0].wit = CTxWitness()
         block.solve()
-        self.nodes[0].submitblock(block.serialize().hex())
+        assert_equal(None, self.nodes[0].submitblock(block.serialize().hex()))
         assert_equal(self.nodes[0].getbestblockhash(), block.hash)
 
         # This time, add a tx with non-empty witness, but don't supply
@@ -997,7 +997,7 @@ class SegWitTest(BitcoinTestFramework):
         block_2.vtx[0].vout.pop()
         block_2.vtx[0].wit = CTxWitness()
 
-        self.nodes[0].submitblock(block_2.serialize().hex())
+        assert_equal('bad-txnmrklroot', self.nodes[0].submitblock(block_2.serialize().hex()))
         # Tip should not advance!
         assert self.nodes[0].getbestblockhash() != block_2.hash