diff --git a/src/expr.c b/src/expr.c
index 7a80ca6..f79af48 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -277,7 +277,7 @@ apfl_expr_move(struct apfl_expr *in)
     do {                               \
         MOVEPTR(out.items, in->items); \
         out.len = in->len;             \
-        out.len = 0;                   \
+        in->len = 0;                   \
     } while (0)
 
 struct apfl_expr_list