diff --git a/IPython/core/displayhook.py b/IPython/core/displayhook.py
index 9890b3d..4949893 100644
--- a/IPython/core/displayhook.py
+++ b/IPython/core/displayhook.py
@@ -25,6 +25,9 @@ from __future__ import print_function
 
 import __builtin__
 
+import sys
+
+
 from IPython.config.configurable import Configurable
 from IPython.utils import io
 from IPython.utils.traitlets import Instance, List
@@ -266,5 +269,7 @@ class DisplayHook(Configurable):
             self.shell.user_ns.update({'_':None,'__':None, '___':None})
         import gc
         # TODO: Is this really needed?
-        gc.collect()
+        # IronPython blocks here forever
+        if sys.platform != "cli":
+            gc.collect()
 
diff --git a/IPython/utils/traitlets.py b/IPython/utils/traitlets.py
index c45d717..2f0ebe2 100644
--- a/IPython/utils/traitlets.py
+++ b/IPython/utils/traitlets.py
@@ -927,11 +927,15 @@ else:
         def validate(self, obj, value):
             if isinstance(value, int):
                 return value
-            elif isinstance(value, long):
+            if isinstance(value, long):
                 # downcast longs that fit in int:
                 # note that int(n > sys.maxint) returns a long, so
                 # we don't need a condition on this cast
                 return int(value)
+            if sys.platform == "cli":
+                from System import Int64
+                if isinstance(value, Int64):
+                    return int(value)
             self.error(obj, value)