diff --git a/db/db_impl.cc b/db/db_impl.cc
index 6cf9e7d09..c2f1ba3dd 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -3682,8 +3682,8 @@ bool DBImpl::MCOverlap(ManualCompaction* m, ManualCompaction* m1) {
   return true;
 }
 
-uint64_t DBImpl::GetWalPreallocateBlockSize(uint64_t write_buffer_size) const {
-  uint64_t bsize = write_buffer_size / 10 + write_buffer_size;
+size_t DBImpl::GetWalPreallocateBlockSize(uint64_t write_buffer_size) const {
+  size_t bsize = write_buffer_size / 10 + write_buffer_size;
   // Some users might set very high write_buffer_size and rely on
   // max_total_wal_size or other parameters to control the WAL size.
   if (db_options_.max_total_wal_size > 0) {
diff --git a/db/db_impl.h b/db/db_impl.h
index 277e09bfd..49c3a1584 100644
--- a/db/db_impl.h
+++ b/db/db_impl.h
@@ -1068,7 +1068,7 @@ class DBImpl : public DB {
   bool HaveManualCompaction(ColumnFamilyData* cfd);
   bool MCOverlap(ManualCompaction* m, ManualCompaction* m1);
 
-  uint64_t GetWalPreallocateBlockSize(uint64_t write_buffer_size) const;
+  size_t GetWalPreallocateBlockSize(uint64_t write_buffer_size) const;
 };
 
 // Sanitize db options.  The caller should delete result.info_log if