diff --git a/degesch.c b/degesch.c
index 5822bb6..5dce5a9 100644
--- a/degesch.c
+++ b/degesch.c
@@ -10484,13 +10484,13 @@ spawn_helper_child (struct app_context *ctx)
 }
 
 static void
-launch_backlog_helper (struct app_context *ctx, FILE *backlog)
+launch_backlog_helper (struct app_context *ctx, int backlog_fd)
 {
 	hard_assert (!ctx->running_backlog_helper);
 	switch (spawn_helper_child (ctx))
 	{
 	case 0:
-		dup2 (fileno (backlog), STDIN_FILENO);
+		dup2 (backlog_fd, STDIN_FILENO);
 		execl ("/bin/sh", "/bin/sh", "-c", get_config_string
 			(ctx->config.root, "behaviour.backlog_helper"), NULL);
 		print_error ("%s: %s",
@@ -10522,7 +10522,7 @@ display_backlog (struct app_context *ctx)
 
 	rewind (backlog);
 	set_cloexec (fileno (backlog));
-	launch_backlog_helper (ctx, backlog);
+	launch_backlog_helper (ctx, fileno (backlog));
 	fclose (backlog);
 }
 
@@ -10544,7 +10544,7 @@ display_full_log (struct app_context *ctx)
 		fflush (ctx->current_buffer->log_file);
 
 	set_cloexec (fileno (full_log));
-	launch_backlog_helper (ctx, full_log);
+	launch_backlog_helper (ctx, fileno (full_log));
 	fclose (full_log);
 }