diff --git a/include/ceres/solver.h b/include/ceres/solver.h
index 6d9cee9..2141cc4 100644
--- a/include/ceres/solver.h
+++ b/include/ceres/solver.h
@@ -191,6 +191,11 @@
     // Maximum number of trial step size iterations during each line search,
     // if a step size satisfying the search conditions cannot be found within
     // this number of trials, the line search will terminate.
+    //
+    // The minimum allowed value is 0 for trust region minimizer and 1
+    // otherwise. If 0 is specified for the trust region minimizer,
+    // the line search use when solving constrained optimization
+    // problems will be disabled.
     int max_num_line_search_step_size_iterations = 20;
 
     // Maximum number of restarts of the line search direction algorithm before
diff --git a/internal/ceres/solver.cc b/internal/ceres/solver.cc
index 65ddf5b..0627d8c 100644
--- a/internal/ceres/solver.cc
+++ b/internal/ceres/solver.cc
@@ -239,7 +239,8 @@
   OPTION_LT_OPTION(max_line_search_step_contraction,
                    min_line_search_step_contraction);
   OPTION_LE(min_line_search_step_contraction, 1.0);
-  OPTION_GT(max_num_line_search_step_size_iterations, 0);
+  OPTION_GE(max_num_line_search_step_size_iterations,
+            (options.minimizer_type == ceres::TRUST_REGION ? 0 : 1));
   OPTION_GT(line_search_sufficient_function_decrease, 0.0);
   OPTION_LT_OPTION(line_search_sufficient_function_decrease,
                    line_search_sufficient_curvature_decrease);
diff --git a/internal/ceres/trust_region_minimizer.cc b/internal/ceres/trust_region_minimizer.cc
index 5505cbb..aacd991 100644
--- a/internal/ceres/trust_region_minimizer.cc
+++ b/internal/ceres/trust_region_minimizer.cc
@@ -93,7 +93,8 @@
       continue;
     }
 
-    if (options_.is_constrained) {
+    if (options_.is_constrained &&
+        options_.max_num_line_search_step_size_iterations > 0) {
       // Use a projected line search to enforce the bounds constraints
       // and improve the quality of the step.
       DoLineSearch(x_, gradient_, x_cost_, &delta_);