diff --git a/gns3server/compute/qemu/qemu_vm.py b/gns3server/compute/qemu/qemu_vm.py
index 3b55e235..d175f35f 100644
--- a/gns3server/compute/qemu/qemu_vm.py
+++ b/gns3server/compute/qemu/qemu_vm.py
@@ -1864,12 +1864,12 @@ class QemuVM(BaseNode):
                     if retcode == 3:
                         # image has leaked clusters, but is not corrupted, let's try to fix it
                         log.warning("Qemu image {} has leaked clusters".format(disk_image))
-                        if (await self._qemu_img_exec([qemu_img_path, "check", "-r", "leaks", "{}".format(disk_image)])) == 3:
+                        if await self._qemu_img_exec([qemu_img_path, "check", "-r", "leaks", "{}".format(disk_image)]) == 3:
                             self.project.emit("log.warning", {"message": "Qemu image '{}' has leaked clusters and could not be fixed".format(disk_image)})
                     elif retcode == 2:
                         # image is corrupted, let's try to fix it
                         log.warning("Qemu image {} is corrupted".format(disk_image))
-                        if (await self._qemu_img_exec([qemu_img_path, "check", "-r", "all", "{}".format(disk_image)])) == 2:
+                        if await self._qemu_img_exec([qemu_img_path, "check", "-r", "all", "{}".format(disk_image)]) == 2:
                             self.project.emit("log.warning", {"message": "Qemu image '{}' is corrupted and could not be fixed".format(disk_image)})
                     # ignore retcode == 1.  One reason is that the image is encrypted and there is no encrypt.key-secret available
                 except (OSError, subprocess.SubprocessError) as e:
@@ -1882,13 +1882,16 @@ class QemuVM(BaseNode):
                     # create the disk
                     await self._create_linked_clone(disk_name, disk_image, disk)
                 else:
+                    backing_file_format = await self._find_disk_file_format(disk_image)
+                    if not backing_file_format:
+                        raise QemuError("Could not detect format for disk image: {}".format(disk_image))
                     # Rebase the image. This is in case the base image moved to a different directory,
                     # which will be the case if we imported a portable project.  This uses
                     # get_abs_image_path(hdX_disk_image) and ignores the old base path embedded
                     # in the qcow2 file itself.
                     try:
                         qcow2 = Qcow2(disk)
-                        await qcow2.rebase(qemu_img_path, disk_image)
+                        await qcow2.rebase(qemu_img_path, disk_image, backing_file_format)
                     except (Qcow2Error, OSError) as e:
                         raise QemuError("Could not use qcow2 disk image '{}' for {}: {}".format(disk_image, disk_name, e))
 
diff --git a/gns3server/compute/qemu/utils/qcow2.py b/gns3server/compute/qemu/utils/qcow2.py
index 719face0..6ce13969 100644
--- a/gns3server/compute/qemu/utils/qcow2.py
+++ b/gns3server/compute/qemu/utils/qcow2.py
@@ -118,18 +118,19 @@ class Qcow2:
         except Qcow2Error:
             return (base_image, None)  # non-qcow2 base images are acceptable (e.g. vmdk, raw image)
 
-    async def rebase(self, qemu_img, base_image):
+    async def rebase(self, qemu_img, base_image, backing_file_format):
         """
         Rebase a linked clone in order to use the correct disk
 
         :param qemu_img: Path to the qemu-img binary
         :param base_image: Path to the base image
+        :param backing_file_format: File format of the base image
         """
 
         if not os.path.exists(base_image):
             raise FileNotFoundError(base_image)
         backing_options, _ = Qcow2.backing_options(base_image)
-        command = [qemu_img, "rebase", "-u", "-b", backing_options, self._path]
+        command = [qemu_img, "rebase", "-u", "-b", backing_options, "-F", backing_file_format, self._path]
         process = await asyncio.create_subprocess_exec(*command)
         retcode = await process.wait()
         if retcode != 0:
diff --git a/tests/compute/qemu/test_qcow2.py b/tests/compute/qemu/test_qcow2.py
index f437fc63..d185135b 100644
--- a/tests/compute/qemu/test_qcow2.py
+++ b/tests/compute/qemu/test_qcow2.py
@@ -73,5 +73,5 @@ async def test_rebase(loop, tmpdir):
     qcow2 = Qcow2(str(tmpdir / "linked.qcow2"))
     assert qcow2.version == 3
     assert qcow2.backing_file == "empty8G.qcow2"
-    await qcow2.rebase(qemu_img(), str(tmpdir / "empty16G.qcow2"))
+    await qcow2.rebase(qemu_img(), str(tmpdir / "empty16G.qcow2"), "qcow2")
     assert qcow2.backing_file == str(tmpdir / "empty16G.qcow2")