diff -rup a/expr.c b/expr.c
--- a/expr.c	2013-10-10 08:43:55.000000000 -0400
+++ b/expr.c	2020-02-06 17:05:40.658679755 -0500
@@ -189,10 +189,10 @@ int
 expr_clone(struct expr_node *retp, const struct expr_node *node)
 {
 	*retp = *node;
+	struct expr_node *nlhs;
+	struct expr_node *nrhs = NULL;
 
 	switch (node->kind) {
-		struct expr_node *nlhs;
-		struct expr_node *nrhs;
 
 	case EXPR_OP_ARGNO:
 	case EXPR_OP_SELF: