diff --git a/src/core/ngx_string.h b/src/core/ngx_string.h
index 83ca4ba..c9d5d80 100644
--- a/src/core/ngx_string.h
+++ b/src/core/ngx_string.h
@@ -12,6 +12,7 @@
 
 
 #define ngx_string(str)  { sizeof(str) - 1, str }
+#define ngx_null_string  { 0, NULL }
 
 
 #if (WIN32)