diff --git a/Include/pyport.h b/Include/pyport.h
index df44be6..66726e8 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -295,6 +295,15 @@
 #define Py_IS_INFINITY(X) ((X) && (X)*0.5 == (X))
 #endif
 
+/* Py_IS_INFINITY(X)
+ * Return 1 if float or double arg is an infinity, else 0.
+ * This some archicetcures (windows) have intrisics for this, so a special
+ * macro for this particular test is useful
+ */
+#ifndef Py_IS_FINITE
+#define Py_IS_FINITE(X) (!Py_IS_INFINITY(X) && !Py_IS_NAN(X))
+#endif
+
 /* HUGE_VAL is supposed to expand to a positive double infinity.  Python
  * uses Py_HUGE_VAL instead because some platforms are broken in this
  * respect.  We used to embed code in pyport.h to try to worm around that,
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 7650ae6..fa09084 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -384,7 +384,7 @@
 	if (PyFloat_Check(w))
 		j = PyFloat_AS_DOUBLE(w);
 
-	else if (Py_IS_INFINITY(i) || Py_IS_NAN(i)) {
+	else if (!Py_IS_FINITE(i)) {
 		if (PyInt_Check(w) || PyLong_Check(w))
 			/* If i is an infinity, its magnitude exceeds any
 			 * finite integer, so it doesn't matter which int we
@@ -802,10 +802,7 @@
 		 * bug; we let that slide in math.pow() (which currently
 		 * reflects all platform accidents), but not for Python's **.
 		 */
-		 if (iv == -1.0 && !Py_IS_INFINITY(iw) && iw == iw) {
-		 	/* XXX the "iw == iw" was to weed out NaNs.  This
-		 	 * XXX doesn't actually work on all platforms.
-		 	 */
+		 if (iv == -1.0 && Py_IS_FINITE(iw)) {
 		 	/* Return 1 if iw is even, -1 if iw is odd; there's
 		 	 * no guarantee that any C integral type is big
 		 	 * enough to hold iw, so we have to check this
diff --git a/PC/pyconfig.h b/PC/pyconfig.h
index a9c1613..cb42131 100644
--- a/PC/pyconfig.h
+++ b/PC/pyconfig.h
@@ -162,6 +162,7 @@
 #include <float.h>
 #define Py_IS_NAN _isnan
 #define Py_IS_INFINITY(X) (!_finite(X) && !_isnan(X))
+#define Py_IS_FINITE(X) _finite(X)
 
 #endif /* _MSC_VER */