diff --git a/builder.py b/builder.py
index b30c363..7aa5d93 100644
--- a/builder.py
+++ b/builder.py
@@ -1334,6 +1334,9 @@ class CExternal(object):
     All class attributes that are `llvm.core.FunctionType` are converted
     to `CFunc` instance during instantiation.
     '''
+
+    _calling_convention_ = None # default
+
     def __init__(self, cbuilder):
         is_func = lambda x: isinstance(x, lc.FunctionType)
         non_magic = lambda s: not ( s.startswith('__') and s.endswith('__') )
@@ -1347,6 +1350,9 @@ class CExternal(object):
         mod = cbuilder.function.module
         for fname, ftype in to_declare:
             func = mod.get_or_insert_function(ftype, name=fname)
+            if self._calling_convention_:
+                func.calling_convention = self._calling_convention_
+
             if func.type.pointee != ftype:
                 raise NameError("Function has already been declared "
                                 "with a different type: %s != %s"