fix English grammar
diff --git a/src/http/ngx_http_upstream.h b/src/http/ngx_http_upstream.h
index de1a2c8..d95399f 100644
--- a/src/http/ngx_http_upstream.h
+++ b/src/http/ngx_http_upstream.h
@@ -244,7 +244,7 @@
     ngx_http_cleanup_pt            *cleanup;
 
     unsigned                        store:1;
-    unsigned                        cachable:1;
+    unsigned                        cacheable:1;
     unsigned                        accel:1;
 
     unsigned                        buffering:1;