diff --git a/common/json.c b/common/json.c
index 2f372044c..b3cb20490 100644
--- a/common/json.c
+++ b/common/json.c
@@ -762,3 +762,9 @@ void json_add_tok(struct json_stream *result, const char *fieldname,
 	}
 	abort();
 }
+
+void json_add_errcode(struct json_stream *result, const char *fieldname,
+		      errcode_t code)
+{
+	json_add_member(result, fieldname, false, "%"PRIerrcode, code);
+}
diff --git a/common/json.h b/common/json.h
index 4ac74bdd9..056e79d41 100644
--- a/common/json.h
+++ b/common/json.h
@@ -264,5 +264,9 @@ void json_add_preimage(struct json_stream *result, const char *fieldname,
 void json_add_tok(struct json_stream *result, const char *fieldname,
                   const jsmntok_t *tok, const char *buffer);
 
+/* Add an error code */
+void json_add_errcode(struct json_stream *result, const char *fieldname,
+		      errcode_t code);
+
 
 #endif /* LIGHTNING_COMMON_JSON_H */