diff --git a/src/dmaster.c b/src/dmaster.c
index 45331c8..2e99c57 100644
--- a/src/dmaster.c
+++ b/src/dmaster.c
@@ -102,9 +102,9 @@ static void setup_daemon(void) {
 
         setup_pidfile();
 
-        close(STDIN_FILENO);
-        close(STDOUT_FILENO);
-        close(STDERR_FILENO);
+        freopen("/dev/null", "r", stdin);
+        freopen("/dev/null", "w", stdout);
+        freopen("/dev/null", "w", stderr);
     }
 }
 
diff --git a/src/dslave.c b/src/dslave.c
index dd373cf..4ae7624 100644
--- a/src/dslave.c
+++ b/src/dslave.c
@@ -100,6 +100,9 @@ static void handle_op_message(uint32_t in_type, struct strbuf *in, struct strbuf
     if (spawnvem(op->path, argv, envp, in, out, 0))
         fatal("child %s failed", op->path);
 
+    if (!out->len)
+        fatal("no response from op");
+
     free_env(envp);
 }