diff --git a/rugnux/RugnuxStills.cpp b/rugnux/RugnuxStills.cpp
index 63a4d14a0..ac0e8e139 100644
--- a/rugnux/RugnuxStills.cpp
+++ b/rugnux/RugnuxStills.cpp
@@ -282,9 +282,9 @@ void Rugnux::RefineStillsGeometry(int start_image, int end_image, int images_to_
     // short, with the cell absorbing it, mispredicted the spots past 2.5 A by enough to make the merged
     // intensities there negative. A deposited cell is often a percent off this crystal (another
     // temperature, or the cell the depositors started from), and a stated distance can be off as much,
-    // so the cell (-C) and the distance (the file's, --detector-distance or DecideStillsGeometry's) are
-    // both only where the fit starts.
-    gr_settings.refine_distance = true;
+    // so the cell (-C) and the file's distance (or DecideStillsGeometry's) are both only where the fit
+    // starts. A distance the user gave (--detector-distance) is held: the cell alone absorbs any error.
+    gr_settings.refine_distance = !config_.detector_distance_given;
     gr_settings.cell_reg_coeff = 0.0;
 
     const DiffractionGeometry nominal = experiment_.GetDiffractionGeometry();