diff --git a/process/JFJochProcess.cpp b/process/JFJochProcess.cpp
index 9a6f424d..c9ada9e8 100644
--- a/process/JFJochProcess.cpp
+++ b/process/JFJochProcess.cpp
@@ -560,6 +560,11 @@ ProcessResult JFJochProcess::Run(JFJochProcessObserver *observer) {
             std::vector<MergedReflection> merged;
             MergeStatistics statistics;
         };
+        // The reference path computes each image's G once (per-image scaling against the
+        // reference); the scaling loop below is skipped, so G is stable across the two passes.
+        // Smoothing it more than once would compound the correction, so do it only on the first
+        // pass. The no-reference path recomputes G from scratch each pass and re-smooths correctly.
+        bool reference_g_smoothed = false;
         auto scale_and_merge = [&](const std::string &label) -> ScaleMergeResult {
             // ScaleOnTheFly self-scaling is only for the no-reference path; with a reference each
             // image is already scaled against it during the per-image pass, so we merge directly.
@@ -580,7 +585,8 @@ ProcessResult JFJochProcess::Run(JFJochProcessObserver *observer) {
             const double smooth_g_deg = experiment_.GetScalingSettings().GetSmoothGDegrees();
             const auto gonio = experiment_.GetGoniometer();
             const double osc_deg = gonio ? std::fabs(gonio->GetIncrement_deg()) : 0.0;
-            if (rot3d && smooth_g_deg > 0.0 && osc_deg > 1e-6) {
+            const bool reference_path = !config_.reference_data.empty();
+            if (rot3d && smooth_g_deg > 0.0 && osc_deg > 1e-6 && !(reference_path && reference_g_smoothed)) {
                 int window = std::max(1, static_cast<int>(std::lround(smooth_g_deg / osc_deg)));
                 if (window % 2 == 0)
                     ++window;   // odd window for a centered average
@@ -588,6 +594,7 @@ ProcessResult JFJochProcess::Run(JFJochProcessObserver *observer) {
                 logger.Info("Smoothing per-frame scale G over {:.2f} deg ({} frames at {:.3f} deg/frame)",
                             smooth_g_deg, window, osc_deg);
                 SmoothImageScaleG(indexer->GetIntegrationOutcome(), window, logger);
+                reference_g_smoothed = true;
             }
             std::vector<IntegrationOutcome> combined;
             if (rot3d) {