diff --git a/dart/lib/header.dart b/dart/lib/header.dart
index 57fe656..3b65cfb 100644
--- a/dart/lib/header.dart
+++ b/dart/lib/header.dart
@@ -215,7 +215,7 @@ class SweepstoreWorkerTicket {
 
   // Offset 0 - 4 bytes
   int get identifier {
-    _concurrencyHeader._header._file.lockSync(FileLock.shared, _baseOffset, _baseOffset + 4);
+    _concurrencyHeader._header._file.lockSync(FileLock.blockingShared, _baseOffset, _baseOffset + 4);
     _concurrencyHeader._header._file.setPositionSync(_baseOffset);
     int id = _concurrencyHeader._header._file.readIntSync(4);
     _concurrencyHeader._header._file.unlockSync(_baseOffset, _baseOffset + 4);
@@ -224,7 +224,7 @@ class SweepstoreWorkerTicket {
 
   // Offset 4 - 4 bytes
   int get workerHeartbeat {
-    _concurrencyHeader._header._file.lockSync(FileLock.shared, _baseOffset + 4, _baseOffset + 8);
+    _concurrencyHeader._header._file.lockSync(FileLock.blockingShared, _baseOffset + 4, _baseOffset + 8);
     _concurrencyHeader._header._file.setPositionSync(_baseOffset + 4);
     int heartbeat = _concurrencyHeader._header._file.readIntSync(4);
     _concurrencyHeader._header._file.unlockSync(_baseOffset + 4, _baseOffset + 8);
@@ -233,7 +233,7 @@ class SweepstoreWorkerTicket {
 
   // Offset 8 - 1 byte
   SweepstoreTicketState get ticketState {
-    _concurrencyHeader._header._file.lockSync(FileLock.shared, _baseOffset + 8, _baseOffset + 9);
+    _concurrencyHeader._header._file.lockSync(FileLock.blockingShared, _baseOffset + 8, _baseOffset + 9);
     _concurrencyHeader._header._file.setPositionSync(_baseOffset + 8);
     int stateValue = _concurrencyHeader._header._file.readIntSync(1);
     _concurrencyHeader._header._file.unlockSync(_baseOffset + 8, _baseOffset + 9);
@@ -242,7 +242,7 @@ class SweepstoreWorkerTicket {
 
   // Offset 9 - 1 byte
   SweepstoreTicketOperation get ticketOperation {
-    _concurrencyHeader._header._file.lockSync(FileLock.shared, _baseOffset + 9, _baseOffset + 10);
+    _concurrencyHeader._header._file.lockSync(FileLock.blockingShared, _baseOffset + 9, _baseOffset + 10);
     _concurrencyHeader._header._file.setPositionSync(_baseOffset + 9);
     int operationValue = _concurrencyHeader._header._file.readIntSync(1);
     _concurrencyHeader._header._file.unlockSync(_baseOffset + 9, _baseOffset + 10);
@@ -251,7 +251,7 @@ class SweepstoreWorkerTicket {
 
   // Offset 10 - 8 bytes
   int get keyHash {
-    _concurrencyHeader._header._file.lockSync(FileLock.shared, _baseOffset + 10, _baseOffset + 18);
+    _concurrencyHeader._header._file.lockSync(FileLock.blockingShared, _baseOffset + 10, _baseOffset + 18);
     _concurrencyHeader._header._file.setPositionSync(_baseOffset + 10);
     int hash = _concurrencyHeader._header._file.readIntSync(8);
     _concurrencyHeader._header._file.unlockSync(_baseOffset + 10, _baseOffset + 18);
@@ -260,7 +260,7 @@ class SweepstoreWorkerTicket {
 
   // Offset 18 - 8 bytes
   SweepstorePointer get writePointer {
-    _concurrencyHeader._header._file.lockSync(FileLock.shared, _baseOffset + 18, _baseOffset + 26);
+    _concurrencyHeader._header._file.lockSync(FileLock.blockingShared, _baseOffset + 18, _baseOffset + 26);
     _concurrencyHeader._header._file.setPositionSync(_baseOffset + 18);
     int address = _concurrencyHeader._header._file.readIntSync(8);
     _concurrencyHeader._header._file.unlockSync(_baseOffset + 18, _baseOffset + 26);
@@ -269,7 +269,7 @@ class SweepstoreWorkerTicket {
 
   // Offset 26 - 4 bytes
   int get writeSize {
-    _concurrencyHeader._header._file.lockSync(FileLock.shared, _baseOffset + 26, _baseOffset + 30);
+    _concurrencyHeader._header._file.lockSync(FileLock.blockingShared, _baseOffset + 26, _baseOffset + 30);
     _concurrencyHeader._header._file.setPositionSync(_baseOffset + 26);
     int size = _concurrencyHeader._header._file.readIntSync(4);
     _concurrencyHeader._header._file.unlockSync(_baseOffset + 26, _baseOffset + 30);