diff --git a/image_analysis/scale_merge/RotationScaleMerge.cpp b/image_analysis/scale_merge/RotationScaleMerge.cpp
index 52e4ba05..14748a65 100644
--- a/image_analysis/scale_merge/RotationScaleMerge.cpp
+++ b/image_analysis/scale_merge/RotationScaleMerge.cpp
@@ -594,10 +594,21 @@ void RotationScaleMerge::SmoothMosaicityAndPartiality() {
     // Recompute each partial's partiality from the smoothed mosaicity (same wedge the predictor used).
     // Frames without a mosaicity keep the stored partiality.
     const double wedge = gon ? std::fabs(gon->GetWedge_deg()) : 0.0;
+    // Energy bandwidth broadens each reflection's rocking curve by (dlambda/lambda)*tan(theta_B) on top
+    // of the mosaicity - the same term the predictor adds and the mosaicity fit takes out, so the
+    // partiality recomputed here matches the one integration was based on. sin(theta_B) = lambda/(2d).
+    const double bandwidth_sigma = x.GetBandwidthFWHM().value_or(0.0f) / 2.3548;
+    const double half_wavelength_A = x.GetWavelength_A() / 2.0;
     ParallelChunks(static_cast<int>(partials.size()), nthreads, [&](int lo, int hi) {
         for (int i = lo; i < hi; ++i) {
             auto &o = partials[i];
-            const float mos = mos_smooth[o.frame];
+            float mos = mos_smooth[o.frame];
+            if (bandwidth_sigma > 0.0 && o.d > 0.0f) {
+                const double sin_theta = half_wavelength_A / o.d;
+                const double sigma_bw = (180.0 / PI) * bandwidth_sigma * sin_theta
+                                        / std::sqrt(1.0 - sin_theta * sin_theta);
+                mos = static_cast<float>(std::sqrt(mos * mos + sigma_bw * sigma_bw));
+            }
             if (std::isfinite(mos) && mos > 1e-6f && std::isfinite(o.zeta) && o.zeta > 0.0f
                 && std::isfinite(o.delta_phi))
                 o.partiality = RotationPartiality(o.delta_phi, o.zeta, mos, wedge);