diff --git a/include/jsonwrt.h b/include/jsonwrt.h
index 4587b60a9..396765c24 100644
--- a/include/jsonwrt.h
+++ b/include/jsonwrt.h
@@ -15,6 +15,7 @@ struct ul_jsonwrt {
 };
 
 void ul_jsonwrt_init(struct ul_jsonwrt *fmt, FILE *out, int indent);
+int ul_jsonwrt_is_ready(struct ul_jsonwrt *fmt);
 void ul_jsonwrt_indent(struct ul_jsonwrt *fmt);
 void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type);
 void ul_jsonwrt_close(struct ul_jsonwrt *fmt, int type);
diff --git a/lib/jsonwrt.c b/lib/jsonwrt.c
index 9331dec0e..8ca1d4d9a 100644
--- a/lib/jsonwrt.c
+++ b/lib/jsonwrt.c
@@ -109,6 +109,11 @@ void ul_jsonwrt_init(struct ul_jsonwrt *fmt, FILE *out, int indent)
 	fmt->after_close = 0;
 }
 
+int ul_jsonwrt_is_ready(struct ul_jsonwrt *fmt)
+{
+	return fmt->out == NULL ? 0 : 1;
+}
+
 void ul_jsonwrt_indent(struct ul_jsonwrt *fmt)
 {
 	int i;