diff --git a/inc/math.h b/inc/math.h
index 2eba9f1..dad2884 100644
--- a/inc/math.h
+++ b/inc/math.h
@@ -46,10 +46,8 @@
 
 static inline int32_t isinf(float x)
 {
-	if (x > FLT_MAX)
-		return 1;
-	else if (x < FLT_MIN)
-		return -1;
+	if (!isnan(x) && isnan(x - x))
+		return (x > 0) ? 1 : -1;
 	else
 		return 0;
 }