fix English grammar
diff --git a/src/core/ngx_string.h b/src/core/ngx_string.h
index 3199384..f967951 100644
--- a/src/core/ngx_string.h
+++ b/src/core/ngx_string.h
@@ -28,7 +28,7 @@
     unsigned    len:29;
 
     unsigned    valid:1;
-    unsigned    no_cachable:1;
+    unsigned    no_cacheable:1;
     unsigned    not_found:1;
 
     u_char     *data;