diff --git a/libraries/testing/include/eosio/testing/tester.hpp b/libraries/testing/include/eosio/testing/tester.hpp
index f7316b4170..02f50051aa 100644
--- a/libraries/testing/include/eosio/testing/tester.hpp
+++ b/libraries/testing/include/eosio/testing/tester.hpp
@@ -146,7 +146,8 @@ namespace eosio::testing {
 
    struct produce_block_result_t {
       signed_block_ptr                   block;
-      std::vector<transaction_trace_ptr> traces; // onblock trace first, followed by transaction traces
+      transaction_trace_ptr              onblock_trace;
+      std::vector<transaction_trace_ptr> traces;         // transaction traces
    };
 
    /**
diff --git a/libraries/testing/tester.cpp b/libraries/testing/tester.cpp
index a962662145..32f5cd8790 100644
--- a/libraries/testing/tester.cpp
+++ b/libraries/testing/tester.cpp
@@ -400,9 +400,9 @@ namespace eosio::testing {
       static transaction_trace_ptr onblock_trace;
 
       if( !control->is_building_block() || control->pending_block_time() != next_time ) {
-         res.traces.emplace_back(_start_block( next_time ));
+         res.onblock_trace = _start_block( next_time );
       } else {
-         res.traces.emplace_back(std::move(onblock_trace)); // saved from _start_block call in last _produce_block
+         res.onblock_trace = std::move(onblock_trace); // saved from _start_block call in last _produce_block
       }
 
       if( !skip_pending_trxs ) {