diff --git a/src/usb/lwip/rest.c b/src/usb/lwip/rest.c
index fdcdfe0..6f468f0 100644
--- a/src/usb/lwip/rest.c
+++ b/src/usb/lwip/rest.c
@@ -207,7 +207,8 @@ int rest_execute_route_handler(const rest_request_t *request, rest_route_handler
         response->json = NULL;
         return -1;
     }
-    if (response->status_code == 0 || response->status_code == 200 || response->status_code == 201 || response->status_code == 204) {
+    bool is_json_response = (response->content_type != NULL && strcmp(response->content_type, "application/json") == 0);
+    if (is_json_response && (response->status_code == 0 || response->status_code == 200 || response->status_code == 201 || response->status_code == 204)) {
         char *body = cJSON_PrintUnformatted(response->json);
         cJSON_Delete(response->json);
         response->json = NULL;
@@ -222,6 +223,7 @@ int rest_execute_route_handler(const rest_request_t *request, rest_route_handler
             }
         }
         response->body = body;
+        response->body_len = 0;
     }
     if (response->json != NULL) {
         cJSON_Delete(response->json);
@@ -395,4 +397,4 @@ rest_route_handler_t rest_background_job_pop(void) {
         }
     }
     return NULL;
-}
\ No newline at end of file
+}
diff --git a/src/usb/lwip/rest_server.c b/src/usb/lwip/rest_server.c
index 51ae3d5..ac88fc4 100644
--- a/src/usb/lwip/rest_server.c
+++ b/src/usb/lwip/rest_server.c
@@ -754,7 +754,7 @@ void rest_handle_request(rest_conn_t *conn) {
     rest_debug_dump_payload("request-body", request->body, request->body_len);
 
     if (request->method == REST_HTTP_POST || request->method == REST_HTTP_PUT) {
-        if (!rest_content_type_is_json(request->content_type)) {
+        if (!rest_content_type_is_json(request->content_type) && strncasecmp(request->content_type, "application/x-pem-file", 22) != 0) {
             send_json_error(conn, 415, "content_type_must_be_application_json");
             return;
         }