diff --git a/lib/http/rpc.js b/lib/http/rpc.js
index d056de72..af03cdcd 100644
--- a/lib/http/rpc.js
+++ b/lib/http/rpc.js
@@ -1051,11 +1051,13 @@ RPC.prototype.submitBlock = co(function* submitBlock(args, help) {
 });
 
 RPC.prototype._submitBlock = co(function* _submitBlock(block) {
-  var unlock = yield this.locker.lock();
+  var unlock1 = yield this.locker.lock();
+  var unlock2 = yield this.chain.locker.lock();
   try {
     return yield this.__submitBlock(block);
   } finally {
-    unlock();
+    unlock2();
+    unlock1();
   }
 });
 
@@ -1066,29 +1068,28 @@ RPC.prototype.__submitBlock = co(function* __submitBlock(block) {
 
   prev = yield this.chain.db.getEntry(block.prevBlock);
 
-  if (!prev)
-    return 'rejected: bad-prevblk';
+  if (prev) {
+    state = yield this.chain.getDeployments(block.ts, prev);
 
-  state = yield this.chain.getDeployments(block.ts, prev);
+    // Fix eloipool bug (witness nonce is not present).
+    if (state.hasWitness() && block.getCommitmentHash()) {
+      tx = block.txs[0];
+      if (!tx.hasWitness()) {
+        this.logger.warning('Submitted block had no witness nonce.');
+        this.logger.debug(tx);
 
-  // Fix eloipool bug (witness nonce is not present).
-  if (state.hasWitness() && block.getCommitmentHash()) {
-    tx = block.txs[0];
-    if (!tx.hasWitness()) {
-      this.logger.warning('Submitted block had no witness nonce.');
-      this.logger.debug(tx);
+        // Recreate witness nonce (all zeroes).
+        tx.inputs[0].witness.set(0, encoding.ZERO_HASH);
+        tx.inputs[0].witness.compile();
 
-      // Recreate witness nonce (all zeroes).
-      tx.inputs[0].witness.set(0, encoding.ZERO_HASH);
-      tx.inputs[0].witness.compile();
-
-      tx.refresh();
-      block.refresh();
+        tx.refresh();
+        block.refresh();
+      }
     }
   }
 
   try {
-    entry = yield this.chain.add(block);
+    entry = yield this.chain._add(block);
   } catch (err) {
     if (err.type === 'VerifyError') {
       this.logger.warning('RPC block rejected: %s (%s).',