diff --git a/src/vim.h b/src/vim.h
index 55cb693..5bd1b3c 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2467,6 +2467,10 @@
 # define MAX_OPEN_CHANNELS 0
 #endif
 
+#if defined(WIN32)
+# define MAX_NAMED_PIPE_SIZE 65535
+#endif
+
 /* Options for json_encode() and json_decode. */
 #define JSON_JS		1   /* use JS instead of JSON */
 #define JSON_NO_NONE	2   /* v:none item not allowed */