diff --git a/internal/ceres/linear_least_squares_problems.cc b/internal/ceres/linear_least_squares_problems.cc
index bc6ff00..6c886a1 100644
--- a/internal/ceres/linear_least_squares_problems.cc
+++ b/internal/ceres/linear_least_squares_problems.cc
@@ -573,6 +573,7 @@
   return problem;
 }
 
+namespace {
 bool DumpLinearLeastSquaresProblemToConsole(const string& directory,
                                             int iteration,
                                             const SparseMatrix* A,
@@ -732,6 +733,7 @@
   WriteStringToFileOrDie(matlab_script, matlab_filename);
   return true;
 }
+}  // namespace
 
 bool DumpLinearLeastSquaresProblem(const string& directory,
                                    int iteration,