diff --git a/src/ioslaves/file/file_unix.cpp b/src/ioslaves/file/file_unix.cpp
--- a/src/ioslaves/file/file_unix.cpp
+++ b/src/ioslaves/file/file_unix.cpp
@@ -51,6 +51,12 @@
 //sendfile has different semantics in different platforms
 #if HAVE_SENDFILE && defined Q_OS_LINUX
 #define USE_SENDFILE 1
+// On Linux, write() (and similar system calls) will transfer at most
+// 0x7ffff000 (2,147,479,552) bytes, returning the number of bytes
+// actually transferred.  (This is true on both 32-bit and 64-bit
+// systems.)
+// This includes sendfile
+#define MAX_SENDFILE_BUFF (0x7ffff000)
 #endif
 
 #ifdef USE_SENDFILE
@@ -258,14 +264,14 @@
     char buffer[ MAX_IPC_SIZE ];
     ssize_t n = 0;
 #ifdef USE_SENDFILE
-    bool use_sendfile = buff_src.st_size < 0x7FFFFFFF;
+    bool use_sendfile = true;
 #endif
     bool existing_dest_delete_attempted = false;
     while (1) {
 #ifdef USE_SENDFILE
         if (use_sendfile) {
             off_t sf = processed_size;
-            n = ::sendfile(dest_file.handle(), src_file.handle(), &sf, MAX_IPC_SIZE);
+            n = ::sendfile(dest_file.handle(), src_file.handle(), &sf, MAX_SENDFILE_BUFF);
             processed_size = sf;
             if (n == -1 && (errno == EINVAL || errno == ENOSYS)) {     //not all filesystems support sendfile()
                 // qDebug() << "sendfile() not supported, falling back ";