diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 6a02f81ad5..9f45b07936 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -2666,10 +2666,13 @@ _outPathKey(StringInfo str, const PathKey *node)
 static void
 _outPathTarget(StringInfo str, const PathTarget *node)
 {
+	int refnos_len = node->sortgrouprefs ?
+					 list_length(node->exprs) : 0;
+
 	WRITE_NODE_TYPE("PATHTARGET");
 
 	WRITE_NODE_FIELD(exprs);
-	WRITE_INDEX_ARRAY(sortgrouprefs, list_length(node->exprs));
+	WRITE_INDEX_ARRAY(sortgrouprefs, refnos_len);
 	WRITE_FLOAT_FIELD(cost.startup, "%.2f");
 	WRITE_FLOAT_FIELD(cost.per_tuple, "%.2f");
 	WRITE_INT_FIELD(width);