diff -NarU5 a/Include/pymem.h b/Include/pymem.h
--- a/Include/pymem.h	2016-12-17 15:05:05.000000000 -0500
+++ b/Include/pymem.h	2017-07-20 15:10:18.655330317 -0400
@@ -70,13 +70,13 @@
    would return a pointer with no memory behind it, which would break
    pymalloc. To solve these problems, allocate an extra byte. */
 /* Returns NULL to indicate error if a negative size or size larger than
    Py_ssize_t can represent is supplied.  Helps prevents security holes. */
 #define PyMem_MALLOC(n)		((size_t)(n) > (size_t)PY_SSIZE_T_MAX ? NULL \
-				: malloc((n) ? (n) : 1))
+				: malloc((n) > 0 ? (n) : 1))
 #define PyMem_REALLOC(p, n)	((size_t)(n) > (size_t)PY_SSIZE_T_MAX  ? NULL \
-				: realloc((p), (n) ? (n) : 1))
+				: realloc((p), (n) > 0 ? (n) : 1))
 #define PyMem_FREE		free
 
 #endif	/* PYMALLOC_DEBUG */
 
 /*