diff --git a/image_analysis/scale_merge/ScaleAndMerge.cpp b/image_analysis/scale_merge/ScaleAndMerge.cpp
index e9102f04..7a4eba1b 100644
--- a/image_analysis/scale_merge/ScaleAndMerge.cpp
+++ b/image_analysis/scale_merge/ScaleAndMerge.cpp
@@ -347,6 +347,7 @@ namespace {
         options.max_num_iterations = opt.max_num_iterations;
         options.max_solver_time_in_seconds = opt.max_solver_time_s;
         options.num_threads = static_cast<int>(hw);
+        options.max_num_iterations = 10; // 6 is usually enough to converge
 
         ceres::Solver::Summary summary;
         ceres::Solve(options, &problem, &summary);