diff --git a/xpath.c b/xpath.c
index 5211b126..f4406967 100644
--- a/xpath.c
+++ b/xpath.c
@@ -524,7 +524,7 @@ xmlXPathIsNaN(double val) {
 int
 xmlXPathIsInf(double val) {
 #ifdef isinf
-    return isinf(val);
+    return isinf(val) ? (val > 0 ? 1 : -1) : 0;
 #else
     if (val >= HUGE_VAL)
         return 1;