diff --git a/src/drivers/px4flow/px4flow.cpp b/src/drivers/px4flow/px4flow.cpp
index 84b9ef00e0..75b859016b 100644
--- a/src/drivers/px4flow/px4flow.cpp
+++ b/src/drivers/px4flow/px4flow.cpp
@@ -141,7 +141,7 @@ private:
 	perf_counter_t		_sample_perf;
 	perf_counter_t		_comms_errors;
 
-	int                 _conversion_interval;
+	unsigned                 _conversion_interval;
 	enum Rotation       _sensor_rotation;
 
 	/**