diff --git a/include/portable.nt b/include/portable.nt
index 9dea2a2c7c..df594f163d 100644
--- a/include/portable.nt
+++ b/include/portable.nt
@@ -56,7 +56,8 @@
 /* define type for caddr_t */
 typedef char * caddr_t;
 
-#define ssize_t signed int
+/* define type for ssize_t */
+typedef signed int ssize_t;
 
 /* we have NT threads */
 #ifdef _MT