diff --git a/savevm.c b/savevm.c
index bf4d0e76c315c3a5d0715b2fa109c9e0c60e2e36..aa6fef08ab68ffc7876a251f1e1f677cdb6d94d9 100644
--- a/savevm.c
+++ b/savevm.c
@@ -455,6 +455,7 @@ void qemu_fflush(QEMUFile *f)
 static void qemu_fill_buffer(QEMUFile *f)
 {
     int len;
+    int pending;
 
     if (!f->get_buffer)
         return;
@@ -462,10 +463,17 @@ static void qemu_fill_buffer(QEMUFile *f)
     if (f->is_write)
         abort();
 
-    len = f->get_buffer(f->opaque, f->buf, f->buf_offset, IO_BUF_SIZE);
+    pending = f->buf_size - f->buf_index;
+    if (pending > 0) {
+        memmove(f->buf, f->buf + f->buf_index, pending);
+    }
+    f->buf_index = 0;
+    f->buf_size = pending;
+
+    len = f->get_buffer(f->opaque, f->buf + pending, f->buf_offset,
+                        IO_BUF_SIZE - pending);
     if (len > 0) {
-        f->buf_index = 0;
-        f->buf_size = len;
+        f->buf_size += len;
         f->buf_offset += len;
     } else if (len != -EAGAIN)
         f->has_error = 1;