diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index edbd09f9425..e3e29f51186 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -1784,7 +1784,7 @@ _outRelOptInfo(StringInfo str, const RelOptInfo *node)
 	WRITE_NODE_FIELD(cheapest_unique_path);
 	WRITE_NODE_FIELD(cheapest_parameterized_paths);
 	WRITE_UINT_FIELD(relid);
-	WRITE_UINT_FIELD(reltablespace);
+	WRITE_OID_FIELD(reltablespace);
 	WRITE_ENUM_FIELD(rtekind, RTEKind);
 	WRITE_INT_FIELD(min_attr);
 	WRITE_INT_FIELD(max_attr);