diff --git a/selfdrive/loggerd/bootlog.cc b/selfdrive/loggerd/bootlog.cc
index e15d84c5db..3f01b9515e 100644
--- a/selfdrive/loggerd/bootlog.cc
+++ b/selfdrive/loggerd/bootlog.cc
@@ -22,13 +22,6 @@ int main(int argc, char** argv) {
   std::string path = LOG_ROOT + "/boot/" + std::string(filename);
   LOGW("bootlog to %s", path.c_str());
 
-  MessageBuilder boot_msg;
-  logger_build_boot(boot_msg);
-
-  MessageBuilder init_msg;
-  logger_build_init_data(init_msg);
-
-
   // Open bootlog
   int r = logger_mkpath((char*)path.c_str());
   assert(r == 0);
@@ -42,12 +35,14 @@ int main(int argc, char** argv) {
   assert(bzerror == BZ_OK);
 
   // Write initdata
-  auto bytes = init_msg.toBytes();
+  kj::Array<capnp::word> init_msg = logger_build_init_data();
+  auto bytes = init_msg.asBytes();
   BZ2_bzWrite(&bzerror, bz_file, bytes.begin(), bytes.size());
   assert(bzerror == BZ_OK);
 
   // Write bootlog
-  bytes = boot_msg.toBytes();
+  kj::Array<capnp::word> boot_msg = logger_build_boot();
+  bytes = boot_msg.asBytes();
   BZ2_bzWrite(&bzerror, bz_file, bytes.begin(), bytes.size());
   assert(bzerror == BZ_OK);
 
diff --git a/selfdrive/loggerd/logger.cc b/selfdrive/loggerd/logger.cc
index a6f2232682..a61881c78e 100644
--- a/selfdrive/loggerd/logger.cc
+++ b/selfdrive/loggerd/logger.cc
@@ -52,7 +52,8 @@ int logger_mkpath(char* file_path) {
 }
 
 // ***** log metadata *****
-void logger_build_boot(MessageBuilder &msg) {
+kj::Array<capnp::word> logger_build_boot() {
+  MessageBuilder msg;
   auto boot = msg.initEvent().initBoot();
 
   boot.setWallTimeNanos(nanos_since_epoch());
@@ -65,9 +66,11 @@ void logger_build_boot(MessageBuilder &msg) {
 
   std::string launchLog = util::read_file("/tmp/launch_log");
   boot.setLaunchLog(capnp::Text::Reader(launchLog.data(), launchLog.size()));
+  return capnp::messageToFlatArray(msg);
 }
 
-void logger_build_init_data(MessageBuilder &msg) {
+kj::Array<capnp::word> logger_build_init_data() {
+  MessageBuilder msg;
   auto init = msg.initEvent().initInitData();
 
   if (util::file_exists("/EON")) {
@@ -132,12 +135,11 @@ void logger_build_init_data(MessageBuilder &msg) {
       i++;
     }
   }
+  return capnp::messageToFlatArray(msg);
 }
 
 void log_init_data(LoggerState *s) {
-  MessageBuilder msg;
-  logger_build_init_data(msg);
-  auto bytes = msg.toBytes();
+  auto bytes = s->init_data.asBytes();
   logger_log(s, bytes.begin(), bytes.size(), s->has_qlog);
 }
 
@@ -154,8 +156,6 @@ static void log_sentinel(LoggerState *s, cereal::Sentinel::SentinelType type) {
 // ***** logging functions *****
 
 void logger_init(LoggerState *s, const char* log_name, bool has_qlog) {
-  memset(s, 0, sizeof(*s));
-
   umask(0);
 
   pthread_mutex_init(&s->lock, NULL);
@@ -170,6 +170,8 @@ void logger_init(LoggerState *s, const char* log_name, bool has_qlog) {
   strftime(s->route_name, sizeof(s->route_name),
            "%Y-%m-%d--%H-%M-%S", &timeinfo);
   snprintf(s->log_name, sizeof(s->log_name), "%s", log_name);
+
+  s->init_data = logger_build_init_data();
 }
 
 static LoggerHandle* logger_open(LoggerState *s, const char* root_path) {
diff --git a/selfdrive/loggerd/logger.h b/selfdrive/loggerd/logger.h
index fc05513e5b..f355586661 100644
--- a/selfdrive/loggerd/logger.h
+++ b/selfdrive/loggerd/logger.h
@@ -32,6 +32,7 @@ typedef struct LoggerHandle {
 typedef struct LoggerState {
   pthread_mutex_t lock;
   int part;
+  kj::Array<capnp::word> init_data;
   char route_name[64];
   char log_name[64];
   bool has_qlog;
@@ -41,8 +42,8 @@ typedef struct LoggerState {
 } LoggerState;
 
 int logger_mkpath(char* file_path);
-void logger_build_boot(MessageBuilder &msg);
-void logger_build_init_data(MessageBuilder &msg);
+kj::Array<capnp::word> logger_build_boot();
+kj::Array<capnp::word> logger_build_init_data();
 void logger_init(LoggerState *s, const char* log_name, bool has_qlog);
 int logger_next(LoggerState *s, const char* root_path,
                             char* out_segment_path, size_t out_segment_path_len,
diff --git a/selfdrive/loggerd/loggerd.cc b/selfdrive/loggerd/loggerd.cc
index 862d958047..1d1daa4ba8 100644
--- a/selfdrive/loggerd/loggerd.cc
+++ b/selfdrive/loggerd/loggerd.cc
@@ -161,7 +161,7 @@ private:
 
 struct LoggerdState {
   Context *ctx;
-  LoggerState logger;
+  LoggerState logger = {};
   char segment_path[4096];
   int rotate_segment;
   pthread_mutex_t rotate_lock;