diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index a0229bed3..d017f0907 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -3,6 +3,7 @@
 
 ### 1.0.0-rc.174
 
+* Rugnux masks a patch of detector pixels that reads high on every frame, not only a single hot pixel or a pair.
 * Rugnux: `.hkl` now holds unmerged, scaled full reflections (SHELX HKLF 4) on rotation data, so SHELXL computes Rint itself.
 * Rugnux reads Rigaku d*TREK SMV images (Saturn CCD), including detector 2theta, image orientation and encoded pixel overflows.
 * Rugnux integrates spots that grow wider than the integration disk away from the beam (typical of small molecules at high X-ray energy) over their measured footprint.
diff --git a/docs/CPU_DATA_ANALYSIS_IMAGE.md b/docs/CPU_DATA_ANALYSIS_IMAGE.md
index 153619e6a..43ccfc6c7 100644
--- a/docs/CPU_DATA_ANALYSIS_IMAGE.md
+++ b/docs/CPU_DATA_ANALYSIS_IMAGE.md
@@ -358,9 +358,10 @@ stays on a pixel for $(\Delta\phi + w)/|\zeta|$ of rotation ($w = 5°$, a genero
 which covers fewer than $k_1 = 1 + \lceil (\Delta\phi + w)/(|\zeta|\,\delta) \rceil$ frames sampled
 $\delta$ apart; and $k_B$ is the binomial bound, from the lit rate of the ring's other pixels, that
 fewer than 0.01 pixels of the whole detector reach by chance. A persistent pixel is masked if it
-stands alone (by itself or in a pair — a larger patch is a feature of the scattering, not a
-defect), reads on average at least ten times its ring, and its mean excess is above the Poisson
-bound; a weaker one cannot make an outlier. Pixels holding the detector's error
+reads on average at least ten times its ring and its mean excess is above the Poisson bound; a
+weaker one cannot make an outlier. This holds for a patch of such pixels as for a lone one: a patch
+lit through the whole sweep is stationary in the lab, so it is no reflection of the rotating
+crystal, and a reflection crossing it would read the patch. Pixels holding the detector's error
 value on most frames (already invalid on every frame, but not in the static mask) are masked with
 them. A CCD (no sensor depth: read with an offset, not Poisson) is left alone. One log line says how
 many pixels were masked and why.