diff --git a/IPython/Shell.py b/IPython/Shell.py
index 5454f7b..5fdab89 100644
--- a/IPython/Shell.py
+++ b/IPython/Shell.py
@@ -292,7 +292,9 @@ if HAS_CTYPES:
         """raises the exception, performs cleanup if needed"""
         if not inspect.isclass(exctype):
             raise TypeError("Only types can be raised (not instances)")
-        res = ctypes.pythonapi.PyThreadState_SetAsyncExc(tid,
+        # Explicit cast to c_long is necessary for 64-bit support:
+        # See https://bugs.launchpad.net/ipython/+bug/237073
+        res = ctypes.pythonapi.PyThreadState_SetAsyncExc(ctypes.c_long(tid),
                                                          ctypes.py_object(exctype))
         if res == 0:
             raise ValueError("invalid thread id")