--- xc/config/cf/NetBSD.cf
+++ xc/config/cf/NetBSD.cf
@@ -127,9 +127,12 @@
       (OSMajorVersion == 2 && OSMinorVersion < 99) || \
       (OSMajorVersion < 2))
 #  define LibraryMTDefines	-DUSE_NBSD_THREADLIB
+#  define SystemMTDefines	-D_REENTRANT
+#  define MTSafeAPIDefines	-DXUSE_MTSAFE_API -DXNO_MTSAFE_PWDAPI
+# else
+#  define SystemMTDefines   -D_REENTRANT -D_POSIX_THREAD_SAFE_FUNCTIONS
+#  define MTSafeAPIDefines  -DXUSE_MTSAFE_API
 # endif
-# define SystemMTDefines	-D_REENTRANT
-# define MTSafeAPIDefines	-DXUSE_MTSAFE_API -DXNO_MTSAFE_PWDAPI
 #else 
 # define ThreadedX		NO
 #endif