diff --git a/src/vim9execute.c b/src/vim9execute.c
index dde95b5..d696280 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -4855,6 +4855,7 @@
 					+ iptr->isn_arg.jumparg.jump_arg_off
 					+ STACK_FRAME_SIZE;
 		    type_T *t = ufunc->uf_arg_types[argidx];
+		    CLEAR_POINTER(tv);
 		    tv->v_type = t->tt_type;
 		}