diff -rNu Cython-0.18/Cython/Utility/CythonFunction.c Cython-0.18-jrray/Cython/Utility/CythonFunction.c
--- Cython-0.18/Cython/Utility/CythonFunction.c	2013-01-28 13:32:47.000000000 -0800
+++ Cython-0.18-jrray/Cython/Utility/CythonFunction.c	2013-02-05 11:39:13.021087177 -0800
@@ -554,7 +554,7 @@
     m->defaults = PyMem_Malloc(size);
     if (!m->defaults)
         return PyErr_NoMemory();
-    memset(m->defaults, 0, sizeof(size));
+    memset(m->defaults, 0, size);
     m->defaults_pyobjects = pyobjects;
     return m->defaults;
 }