diff --git a/image_analysis/bragg_integration/ProfileIntegrate2D.cpp b/image_analysis/bragg_integration/ProfileIntegrate2D.cpp
index c43a5d2d..95cfeed1 100644
--- a/image_analysis/bragg_integration/ProfileIntegrate2D.cpp
+++ b/image_analysis/bragg_integration/ProfileIntegrate2D.cpp
@@ -39,6 +39,8 @@ Rough BoxSum(const T *image, size_t xpixel, size_t ypixel, int64_t special, int6
     int64_t I_sum = 0, n_inner = 0, n_inner_valid = 0;
     double bkg_sum = 0.0;
     int n_bkg = 0;
+    std::vector<double> bkg_vals;
+    bkg_vals.reserve(128);
     for (int64_t y = y0; y <= y1; ++y)
         for (int64_t x = x0; x <= x1; ++x) {
             const double d2 = (x - r.predicted_x) * (x - r.predicted_x) + (y - r.predicted_y) * (y - r.predicted_y);
@@ -52,11 +54,23 @@ Rough BoxSum(const T *image, size_t xpixel, size_t ypixel, int64_t special, int6
                 if (px == special || px == special + 1 || px == saturation || px == saturation - 1) continue;
                 bkg_sum += static_cast<double>(px);
                 ++n_bkg;
+                bkg_vals.push_back(static_cast<double>(px));
             }
         }
     if (n_inner_valid != n_inner || n_bkg <= 5)
         return out;
     out.bkg = bkg_sum / n_bkg;
+    // One high-outlier sigma-clip pass on the background ring. A bandwidth-streaked high-resolution spot
+    // (or a neighbour) leaks into the annulus and biases the mean high, which over-subtracts and drives
+    // the merged high-resolution intensities negative; rejecting pixels above mean + 3*sqrt(mean) removes
+    // that contamination (and barely touches a clean Poisson background, where ~0.1% exceed the cut).
+    {
+        const double thr = out.bkg + 3.0 * std::sqrt(std::max(out.bkg, 1.0));
+        double s = 0.0;
+        int n = 0;
+        for (const double v : bkg_vals) if (v <= thr) { s += v; ++n; }
+        if (n > 5) out.bkg = s / n;
+    }
     out.I = static_cast<double>(I_sum) - static_cast<double>(n_inner) * out.bkg;
     out.sigma = std::max(1.0, out.I * min_sigma_ratio);
     if (I_sum > 0)