diff --git a/NTPClient.cpp b/NTPClient.cpp
index 1f62f7f..c68f1c5 100644
--- a/NTPClient.cpp
+++ b/NTPClient.cpp
@@ -26,7 +26,7 @@ void NTPClient::set_server(const char* server, int port) {
     nist_server_port = port;
 }
 
-time_t NTPClient::get_timestamp(int timeout) {
+int64_t NTPClient::get_timestamp(int timeout) {
     const time_t TIME1970 = (time_t)2208988800UL;
     int ntp_send_values[12] = {0};
     int ntp_recv_values[12] = {0};
diff --git a/NTPClient.h b/NTPClient.h
index 8f755f5..000c563 100644
--- a/NTPClient.h
+++ b/NTPClient.h
@@ -23,7 +23,7 @@ class NTPClient {
     public:
         explicit NTPClient(NetworkInterface *interface = NULL);
         void set_server(const char* server, int port);
-        time_t get_timestamp(int timeout = 15000);
+        int64_t get_timestamp(int timeout = 15000);
         void network(NetworkInterface *interface);
 
     private: