diff --git a/Include/pymem.h b/Include/pymem.h
index 542aceef253..c8801bbf052 100644
--- a/Include/pymem.h
+++ b/Include/pymem.h
@@ -90,10 +90,10 @@ PyAPI_FUNC(void) PyMem_Free(void *);
  */
 
 #define PyMem_New(type, n) \
-  ( ((n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL : \
+  ( ((size_t)(n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL :	\
 	( (type *) PyMem_Malloc((n) * sizeof(type)) ) )
 #define PyMem_NEW(type, n) \
-  ( ((n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL : \
+  ( ((size_t)(n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL :	\
 	( (type *) PyMem_MALLOC((n) * sizeof(type)) ) )
 
 /*
@@ -103,10 +103,10 @@ PyAPI_FUNC(void) PyMem_Free(void *);
  * caller's memory error handler to not lose track of it.
  */
 #define PyMem_Resize(p, type, n) \
-  ( (p) = ((n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL : \
+  ( (p) = ((size_t)(n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL :	\
 	(type *) PyMem_Realloc((p), (n) * sizeof(type)) )
 #define PyMem_RESIZE(p, type, n) \
-  ( (p) = ((n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL : \
+  ( (p) = ((size_t)(n) > PY_SSIZE_T_MAX / sizeof(type)) ? NULL :	\
 	(type *) PyMem_REALLOC((p), (n) * sizeof(type)) )
 
 /* PyMem{Del,DEL} are left over from ancient days, and shouldn't be used
diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index aef06495ab3..cb7ba8e6fee 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -1745,14 +1745,14 @@ array_ass_subscr(arrayobject* self, PyObject* item, PyObject* value)
 		     cur += step, i++) {
 			Py_ssize_t lim = step - 1;
 
-			if (cur + step >= Py_SIZE(self))
+			if (cur + step >= (size_t)Py_SIZE(self))
 				lim = Py_SIZE(self) - cur - 1;
 			memmove(self->ob_item + (cur - i) * itemsize,
 				self->ob_item + (cur + 1) * itemsize,
 				lim * itemsize);
 		}
 		cur = start + slicelength * step;
-		if (cur < Py_SIZE(self)) {
+		if (cur < (size_t)Py_SIZE(self)) {
 			memmove(self->ob_item + (cur-slicelength) * itemsize,
 				self->ob_item + cur * itemsize,
 				(Py_SIZE(self) - cur) * itemsize);