diff --git a/contrib/win32/win32compat/fileio.c b/contrib/win32/win32compat/fileio.c
index 3b3a99c41..2cb08557e 100644
--- a/contrib/win32/win32compat/fileio.c
+++ b/contrib/win32/win32compat/fileio.c
@@ -811,7 +811,7 @@ cleanup:
 }
 
 long
-fileio_lseek(struct w32_io* pio, long offset, int origin)
+fileio_lseek(struct w32_io* pio, unsigned __int64 offset, int origin)
 {
 	debug4("lseek - pio:%p", pio);
 	if (origin != SEEK_SET) {
@@ -820,8 +820,9 @@ fileio_lseek(struct w32_io* pio, long offset, int origin)
 		return -1;
 	}
 
-	pio->read_overlapped.Offset = offset;
-	pio->write_overlapped.Offset = offset;
+	pio->write_overlapped.Offset = pio->read_overlapped.Offset = offset & 0xffffffff;
+	pio->write_overlapped.OffsetHigh = pio->read_overlapped.OffsetHigh = (offset & 0xffffffff00000000) >> 32;
+	 
 	return 0;
 }
 
diff --git a/contrib/win32/win32compat/inc/unistd.h b/contrib/win32/win32compat/inc/unistd.h
index 688caae93..25d55c307 100644
--- a/contrib/win32/win32compat/inc/unistd.h
+++ b/contrib/win32/win32compat/inc/unistd.h
@@ -46,7 +46,7 @@ int w32_dup2(int oldfd, int newfd);
 unsigned int w32_alarm(unsigned int seconds);
 #define alarm w32_alarm
 
-long w32_lseek(int fd, long offset, int origin);
+long w32_lseek(int fd, unsigned __int64 offset, int origin);
 #define lseek w32_lseek
 
 #define getdtablesize() MAX_FDS
diff --git a/contrib/win32/win32compat/w32fd.c b/contrib/win32/win32compat/w32fd.c
index 6a9d13293..91394dc6a 100644
--- a/contrib/win32/win32compat/w32fd.c
+++ b/contrib/win32/win32compat/w32fd.c
@@ -484,7 +484,7 @@ w32_fstat(int fd, struct w32_stat *buf)
 }
 
 long
-w32_lseek(int fd, long offset, int origin)
+w32_lseek(int fd, unsigned __int64 offset, int origin)
 {
 	CHECK_FD(fd);
 	return fileio_lseek(fd_table.w32_ios[fd], offset, origin);
diff --git a/contrib/win32/win32compat/w32fd.h b/contrib/win32/win32compat/w32fd.h
index 7bb4335a0..1768a3488 100644
--- a/contrib/win32/win32compat/w32fd.h
+++ b/contrib/win32/win32compat/w32fd.h
@@ -163,5 +163,5 @@ int fileio_read(struct w32_io* pio, void *dst, size_t max);
 int fileio_write(struct w32_io* pio, const void *buf, size_t max);
 int fileio_fstat(struct w32_io* pio, struct _stat64 *buf);
 int fileio_stat(const char *path, struct _stat64 *buf);
-long fileio_lseek(struct w32_io* pio, long offset, int origin);
+long fileio_lseek(struct w32_io* pio, unsigned __int64 offset, int origin);
 FILE* fileio_fdopen(struct w32_io* pio, const char *mode);