diff --git a/gns3server/modules/dynamips/__init__.py b/gns3server/modules/dynamips/__init__.py
index 05023a96..23af464b 100644
--- a/gns3server/modules/dynamips/__init__.py
+++ b/gns3server/modules/dynamips/__init__.py
@@ -105,6 +105,7 @@ class Dynamips(BaseManager):
 
     _VM_CLASS = DynamipsVM
     _DEVICE_CLASS = DynamipsDevice
+    _ghost_ios_lock = asyncio.Lock()
 
     def __init__(self):
 
@@ -347,7 +348,8 @@ class Dynamips(BaseManager):
 
         ghost_ios_support = self.config.get_section_config("Dynamips").getboolean("ghost_ios_support", True)
         if ghost_ios_support:
-            yield from self._set_ghost_ios(vm)
+            with (yield from Dynamips._ghost_ios_lock):
+                yield from self._set_ghost_ios(vm)
 
     @asyncio.coroutine
     def create_nio(self, node, nio_settings):