diff --git a/libraries/AP_HAL_Linux/OpticalFlow_Onboard.cpp b/libraries/AP_HAL_Linux/OpticalFlow_Onboard.cpp
index 981afc77bb..9f597ace53 100644
--- a/libraries/AP_HAL_Linux/OpticalFlow_Onboard.cpp
+++ b/libraries/AP_HAL_Linux/OpticalFlow_Onboard.cpp
@@ -220,7 +220,7 @@ void OpticalFlow_Onboard::push_gyro(float gyro_x, float gyro_y, float dt)
     _integrated_gyro.x += (gyro_x - _gyro_bias.x) * dt;
     _integrated_gyro.y += (gyro_y - _gyro_bias.y) * dt;
     sample.gyro = _integrated_gyro;
-    sample.time_us = 1.0e6 * (ts.tv_sec + (ts.tv_nsec*1.0e-9));
+    sample.time_us = ts.tv_sec*1000000ULL + ts.tv_nsec/1000ULL;
 
     _gyro_ring_buffer->push(sample);
 }