diff --git a/PID_v1/PID_v1.cpp b/PID_v1/PID_v1.cpp
index fa67494..a5a76ae 100644
--- a/PID_v1/PID_v1.cpp
+++ b/PID_v1/PID_v1.cpp
@@ -46,7 +46,7 @@ void PID::Compute()
 {
    if(!inAuto) return;
    unsigned long now = millis();
-   int timeChange = (now - lastTime);
+   unsigned long timeChange = (now - lastTime);
    if(timeChange>=SampleTime)
    {
       /*Compute all the working error variables*/