diff --git a/Lib/test/test_xdrlib.py b/Lib/test/test_xdrlib.py
index 9ba8885..91d4162 100644
--- a/Lib/test/test_xdrlib.py
+++ b/Lib/test/test_xdrlib.py
@@ -51,8 +51,32 @@
         up.done()
         self.assertRaises(EOFError, up.unpack_uint)
 
+class ConversionErrorTest(unittest.TestCase):
+
+    def setUp(self):
+        self.packer = xdrlib.Packer()
+
+    def assertRaisesConversion(self, *args):
+        self.assertRaises(xdrlib.ConversionError, *args)
+
+    def test_pack_int(self):
+        self.assertRaisesConversion(self.packer.pack_int, 'string')
+
+    def test_pack_uint(self):
+        self.assertRaisesConversion(self.packer.pack_uint, 'string')
+
+    def test_float(self):
+        self.assertRaisesConversion(self.packer.pack_float, 'string')
+
+    def test_double(self):
+        self.assertRaisesConversion(self.packer.pack_double, 'string')
+
+    def test_uhyper(self):
+        self.assertRaisesConversion(self.packer.pack_uhyper, 'string')
+
 def test_main():
     test_support.run_unittest(XDRTest)
+    test_support.run_unittest(ConversionErrorTest)
 
 if __name__ == "__main__":
     test_main()
diff --git a/Lib/xdrlib.py b/Lib/xdrlib.py
index ef172dd..7afba49 100644
--- a/Lib/xdrlib.py
+++ b/Lib/xdrlib.py
@@ -9,6 +9,7 @@
     from cStringIO import StringIO as _StringIO
 except ImportError:
     from StringIO import StringIO as _StringIO
+from functools import wraps
 
 __all__ = ["Error", "Packer", "Unpacker", "ConversionError"]
 
@@ -34,6 +35,16 @@
 class ConversionError(Error):
     pass
 
+def raise_conversion_error(function):
+    """ Wrap any raised struct.errors in a ConversionError. """
+
+    @wraps(function)
+    def result(self, value):
+        try:
+            return function(self, value)
+        except struct.error as e:
+            raise ConversionError(e.args[0])
+    return result
 
 
 class Packer:
@@ -50,9 +61,11 @@
     # backwards compatibility
     get_buf = get_buffer
 
+    @raise_conversion_error
     def pack_uint(self, x):
         self.__buf.write(struct.pack('>L', x))
 
+    @raise_conversion_error
     def pack_int(self, x):
         self.__buf.write(struct.pack('>l', x))
 
@@ -63,20 +76,24 @@
         else: self.__buf.write('\0\0\0\0')
 
     def pack_uhyper(self, x):
-        self.pack_uint(x>>32 & 0xffffffffL)
-        self.pack_uint(x & 0xffffffffL)
+        try:
+            self.pack_uint(x>>32 & 0xffffffffL)
+        except (TypeError, struct.error) as e:
+            raise ConversionError(e.args[0])
+        try:
+            self.pack_uint(x & 0xffffffffL)
+        except (TypeError, struct.error) as e:
+            raise ConversionError(e.args[0])
 
     pack_hyper = pack_uhyper
 
+    @raise_conversion_error
     def pack_float(self, x):
-        try: self.__buf.write(struct.pack('>f', x))
-        except struct.error, msg:
-            raise ConversionError, msg
+        self.__buf.write(struct.pack('>f', x))
 
+    @raise_conversion_error
     def pack_double(self, x):
-        try: self.__buf.write(struct.pack('>d', x))
-        except struct.error, msg:
-            raise ConversionError, msg
+        self.__buf.write(struct.pack('>d', x))
 
     def pack_fstring(self, n, s):
         if n < 0: