diff --git a/gns3server/modules/dynamips/nodes/router.py b/gns3server/modules/dynamips/nodes/router.py
index a2328294..411b690c 100644
--- a/gns3server/modules/dynamips/nodes/router.py
+++ b/gns3server/modules/dynamips/nodes/router.py
@@ -400,8 +400,11 @@ class Router(object):
         if not self._image:
             raise DynamipsError("Register an IOS image fist")
 
-        self._hypervisor.send("vm set_tsg {name} {group_id}".format(name=self._name,
-                                                                    group_id=group_id))
+        try:
+            self._hypervisor.send("vm set_tsg {name} {group_id}".format(name=self._name,
+                                                                        group_id=group_id))
+        except DynamipsError:
+            raise DynamipsError("JIT sharing is only supported in Dynamips >= 0.2.8-RC3 unstable")
 
         log.info("router {name} [id={id}]: set in JIT sharing group {group_id}".format(name=self._name,
                                                                                        id=self._id,
diff --git a/setup.py b/setup.py
index ffba880a..17532f33 100644
--- a/setup.py
+++ b/setup.py
@@ -46,7 +46,7 @@ setup(
     long_description=open("README.rst", "r").read(),
     install_requires=[
         "tornado>=3.1",
-        "pyzmq>=14.0.0",
+        "pyzmq>=13.1.0",  # this is the strict minimum, recommended is >= 14.0.0
         "jsonschema==2.3.0"
         ],
     entry_points={