diff --git a/common/DiffractionSpot.cpp b/common/DiffractionSpot.cpp
index dd8fe53d..90ac1181 100644
--- a/common/DiffractionSpot.cpp
+++ b/common/DiffractionSpot.cpp
@@ -70,7 +70,9 @@ SpotToSave DiffractionSpot::Export(const DiffractionGeometry &geometry, int64_t
 
     float phi = 0.0f;
     if (geometry.GetRotation()) {
-        phi = geometry.GetRotation()->GetIncrement_deg() * image_num + geometry.GetRotation()->GetWedge_deg();
+        // Rotation angle is considered as increment + half wedge.
+        // It ignores the starting angle.
+        phi = geometry.GetRotation()->GetAngle_deg(image_num) + geometry.GetRotation()->GetWedge_deg() / 2.0f;
     }
 
     return {