diff --git a/PID_v1/PID_v1.h b/PID_v1/PID_v1.h
index 2b3874f..ef3ea4d 100644
--- a/PID_v1/PID_v1.h
+++ b/PID_v1/PID_v1.h
@@ -72,7 +72,7 @@ class PID
 	unsigned long lastTime;
 	double ITerm, lastInput;
 
-	int SampleTime;
+	unsigned long SampleTime;
 	double outMin, outMax;
 	bool inAuto;
 };