diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index b790777108..0524cb8541 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -6168,7 +6168,7 @@ write_item(const void *data, Size len, FILE *fp)
 {
 	if (fwrite(&len, 1, sizeof(len), fp) != sizeof(len))
 		elog(FATAL, "could not write init file");
-	if (fwrite(data, 1, len, fp) != len)
+	if (len > 0 && fwrite(data, 1, len, fp) != len)
 		elog(FATAL, "could not write init file");
 }