diff --git a/src/evalfunc.c b/src/evalfunc.c
index 6706fe1..7f433a5 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2819,7 +2819,17 @@
 	--list->lv_refcount;
     }
 
-    rettv->vval.v_string = redir_execute_ga.ga_data;
+    /* Need to append a NUL to the result. */
+    if (ga_grow(&redir_execute_ga, 1) == OK)
+    {
+	((char *)redir_execute_ga.ga_data)[redir_execute_ga.ga_len] = NUL;
+	rettv->vval.v_string = redir_execute_ga.ga_data;
+    }
+    else
+    {
+	ga_clear(&redir_execute_ga);
+	rettv->vval.v_string = NULL;
+    }
     msg_silent = save_msg_silent;
     emsg_silent = save_emsg_silent;
     emsg_noredir = save_emsg_noredir;