diff --git a/docs/MERGE_MINING.MD b/docs/MERGE_MINING.MD
index c019c0c..bcadc06 100644
--- a/docs/MERGE_MINING.MD
+++ b/docs/MERGE_MINING.MD
@@ -121,4 +121,4 @@ Field|Description
 
 Example response 1: `{"jsonrpc":"2.0","id":"0","result":{"status":"accepted"}}`
 
-Example response 2: `{"jsonrpc":"2.0","id":"0","error":"something went wrong"}`
+Example response 2: `{"jsonrpc":"2.0","id":"0","error":{"code":-1,"message":"Block not accepted"}}`
diff --git a/src/merge_mining_client_json_rpc.cpp b/src/merge_mining_client_json_rpc.cpp
index ef6350d..a9822ad 100644
--- a/src/merge_mining_client_json_rpc.cpp
+++ b/src/merge_mining_client_json_rpc.cpp
@@ -354,7 +354,17 @@ bool MergeMiningClientJSON_RPC::parse_merge_mining_submit_solution(const char* d
 	}
 
 	if (doc.HasMember("error")) {
-		return err(doc["error"].IsString() ? doc["error"].GetString() : "an unknown error occurred");
+		const auto& error_result = doc["error"];
+
+		if (error_result.IsString()) {
+			return err(error_result.GetString());
+		}
+		else if (error_result.IsObject() && error_result.HasMember("message") && error_result["message"].IsString()) {
+			return err(error_result["message"].GetString());
+		}
+		else {
+			return err("an unknown error occurred");
+		}
 	}
 
 	if (!doc.HasMember("result")) {
@@ -372,6 +382,12 @@ bool MergeMiningClientJSON_RPC::parse_merge_mining_submit_solution(const char* d
 	}
 
 	const char* status = result["status"].GetString();
+
+	// Empty string means no errors and the block was accepted
+	if (strlen(status) == 0) {
+		status = "accepted";
+	}
+
 	LOGINFO(0, log::LightGreen() << "merge_mining_submit_solution to " << m_host << ':' << m_port << ": " << status);
 
 	// Get new mining job
diff --git a/src/miner.cpp b/src/miner.cpp
index cb3bac7..ecd82c6 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -242,12 +242,19 @@ void Miner::run(WorkerData* data)
 		}
 
 		if (j.m_auxDiff.check_pow(h)) {
+			std::vector<p2pool::SubmitAuxBlockData> aux_blocks;
+			aux_blocks.reserve(j.m_auxChains.size());
+
 			for (const AuxChainData& aux_data : j.m_auxChains) {
 				if (aux_data.difficulty.check_pow(h)) {
 					LOGINFO(0, log::Green() << "AUX BLOCK FOUND: chain_id " << aux_data.unique_id << ", diff " << aux_data.difficulty << ", worker thread " << data->m_index << '/' << data->m_count);
-					m_pool->submit_aux_block_async(aux_data.unique_id, j.m_templateId, j.m_nonce, j.m_extraNonce);
+					aux_blocks.emplace_back(p2pool::SubmitAuxBlockData{ aux_data.unique_id, j.m_templateId, j.m_nonce, j.m_extraNonce });
 				}
 			}
+
+			if (!aux_blocks.empty()) {
+				m_pool->submit_aux_block_async(aux_blocks);
+			}
 		}
 
 		if (j.m_sidechainDiff.check_pow(h)) {
diff --git a/src/p2pool.cpp b/src/p2pool.cpp
index 6284245..5eb0742 100644
--- a/src/p2pool.cpp
+++ b/src/p2pool.cpp
@@ -644,11 +644,11 @@ void p2pool::submit_block_async(std::vector<uint8_t>&& blob)
 	}
 }
 
-void p2pool::submit_aux_block_async(const hash& chain_id, uint32_t template_id, uint32_t nonce, uint32_t extra_nonce)
+void p2pool::submit_aux_block_async(const std::vector<SubmitAuxBlockData>& aux_blocks)
 {
 	{
 		MutexLock lock(m_submitAuxBlockDataLock);
-		m_submitAuxBlockData.emplace_back(SubmitAuxBlockData{ chain_id, template_id, nonce, extra_nonce });
+		m_submitAuxBlockData.insert(m_submitAuxBlockData.end(), aux_blocks.begin(), aux_blocks.end());
 	}
 
 	// If p2pool is stopped, m_submitAuxBlockAsync is most likely already closed
@@ -738,7 +738,7 @@ void p2pool::submit_aux_block() const
 					LOGWARN(3, "submit_aux_block: failed to get merkle proof for chain_id " << chain_id);
 				}
 
-				return;
+				break;
 			}
 		}
 	}
diff --git a/src/p2pool.h b/src/p2pool.h
index 73a3b21..561d649 100644
--- a/src/p2pool.h
+++ b/src/p2pool.h
@@ -91,7 +91,15 @@ public:
 	void submit_block_async(uint32_t template_id, uint32_t nonce, uint32_t extra_nonce);
 	void submit_block_async(std::vector<uint8_t>&& blob);
 
-	void submit_aux_block_async(const hash& chain_id, uint32_t template_id, uint32_t nonce, uint32_t extra_nonce);
+	struct SubmitAuxBlockData
+	{
+		hash chain_id;
+		uint32_t template_id = 0;
+		uint32_t nonce = 0;
+		uint32_t extra_nonce = 0;
+	};
+
+	void submit_aux_block_async(const std::vector<SubmitAuxBlockData>& aux_blocks);
 
 	bool submit_sidechain_block(uint32_t template_id, uint32_t nonce, uint32_t extra_nonce);
 
@@ -223,14 +231,6 @@ private:
 	mutable uv_mutex_t m_submitBlockDataLock;
 	SubmitBlockData m_submitBlockData;
 
-	struct SubmitAuxBlockData
-	{
-		hash chain_id;
-		uint32_t template_id = 0;
-		uint32_t nonce = 0;
-		uint32_t extra_nonce = 0;
-	};
-
 	mutable uv_mutex_t m_submitAuxBlockDataLock;
 	mutable std::vector<SubmitAuxBlockData> m_submitAuxBlockData;
 
diff --git a/src/stratum_server.cpp b/src/stratum_server.cpp
index f290ddf..65ed84a 100644
--- a/src/stratum_server.cpp
+++ b/src/stratum_server.cpp
@@ -403,13 +403,22 @@ bool StratumServer::on_submit(StratumClient* client, uint32_t id, const char* jo
 		}
 
 		if (aux_diff.check_pow(resultHash)) {
-			for (const AuxChainData& aux_data : block.get_aux_chains(template_id)) {
+			const std::vector<AuxChainData> aux_chains = block.get_aux_chains(template_id);
+
+			std::vector<p2pool::SubmitAuxBlockData> aux_blocks;
+			aux_blocks.reserve(aux_chains.size());
+
+			for (const AuxChainData& aux_data : aux_chains) {
 				if (aux_data.difficulty.check_pow(resultHash)) {
 					const char* s = client->m_customUser;
 					LOGINFO(0, log::Green() << "client " << static_cast<char*>(client->m_addrString) << (*s ? " user " : "") << s << " found an aux block for chain_id " << aux_data.unique_id << ", diff " << aux_data.difficulty << ", submitting it");
-					m_pool->submit_aux_block_async(aux_data.unique_id, template_id, nonce, extra_nonce);
+					aux_blocks.emplace_back(p2pool::SubmitAuxBlockData{ aux_data.unique_id, template_id, nonce, extra_nonce });
 				}
 			}
+
+			if (!aux_blocks.empty()) {
+				m_pool->submit_aux_block_async(aux_blocks);
+			}
 		}
 
 		SubmittedShare* share;