diff --git a/gns3server/compute/base_manager.py b/gns3server/compute/base_manager.py
index 3e3398a2..b526751d 100644
--- a/gns3server/compute/base_manager.py
+++ b/gns3server/compute/base_manager.py
@@ -557,7 +557,7 @@ class BaseManager:
                     f.write(packet)
             os.chmod(tmp_path, stat.S_IWRITE | stat.S_IREAD | stat.S_IEXEC)
             shutil.move(tmp_path, path)
-            md5sum(path)
+            yield from wait_run_in_executor(md5sum, path)
         except OSError as e:
             raise aiohttp.web.HTTPConflict(text="Could not write image: {} because {}".format(filename, e))
 
diff --git a/gns3server/compute/qemu/qemu_vm.py b/gns3server/compute/qemu/qemu_vm.py
index 76067b5e..73f9d7c0 100644
--- a/gns3server/compute/qemu/qemu_vm.py
+++ b/gns3server/compute/qemu/qemu_vm.py
@@ -32,7 +32,7 @@ import gns3server
 import subprocess
 
 from gns3server.utils import parse_version
-from gns3server.utils.asyncio import subprocess_check_output
+from gns3server.utils.asyncio import subprocess_check_output, wait_run_in_executor
 from .qemu_error import QemuError
 from ..adapters.ethernet_adapter import EthernetAdapter
 from ..nios.nio_udp import NIOUDP