diff --git a/internal/ceres/file.cc b/internal/ceres/file.cc
index 387f359..5226c85 100644
--- a/internal/ceres/file.cc
+++ b/internal/ceres/file.cc
@@ -30,6 +30,8 @@
 //
 // Really simple file IO.
 
+#include "ceres/file.h"
+
 #include <cstdio>
 #include "glog/logging.h"
 
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,
diff --git a/internal/ceres/residual_block_utils.cc b/internal/ceres/residual_block_utils.cc
index ff18e21..4d88a9f 100644
--- a/internal/ceres/residual_block_utils.cc
+++ b/internal/ceres/residual_block_utils.cc
@@ -63,6 +63,7 @@
 
 // Utility routine to print an array of doubles to a string. If the
 // array pointer is NULL, it is treated as an array of zeros.
+namespace {
 void AppendArrayToString(const int size, const double* x, string* result) {
   for (int i = 0; i < size; ++i) {
     if (x == NULL) {
@@ -76,6 +77,7 @@
     }
   }
 }
+}  // namespace
 
 string EvaluationToString(const ResidualBlock& block,
                           double const* const* parameters,
diff --git a/internal/ceres/solver_impl.cc b/internal/ceres/solver_impl.cc
index 7f85fbe..5bcfdc6 100644
--- a/internal/ceres/solver_impl.cc
+++ b/internal/ceres/solver_impl.cc
@@ -1228,8 +1228,8 @@
 // Find the minimum index of any parameter block to the given residual.
 // Parameter blocks that have indices greater than num_eliminate_blocks are
 // considered to have an index equal to num_eliminate_blocks.
-int MinParameterBlock(const ResidualBlock* residual_block,
-                      int num_eliminate_blocks) {
+static int MinParameterBlock(const ResidualBlock* residual_block,
+                             int num_eliminate_blocks) {
   int min_parameter_block_position = num_eliminate_blocks;
   for (int i = 0; i < residual_block->NumParameterBlocks(); ++i) {
     ParameterBlock* parameter_block = residual_block->parameter_blocks()[i];
diff --git a/internal/ceres/split.cc b/internal/ceres/split.cc
index 4fa1bd4..3edbc28 100644
--- a/internal/ceres/split.cc
+++ b/internal/ceres/split.cc
@@ -28,6 +28,8 @@
 //
 // Author: keir@google.com (Keir Mierle)
 
+#include "ceres/split.h"
+
 #include <string>
 #include <vector>
 #include <iterator>
diff --git a/internal/ceres/stringprintf.cc b/internal/ceres/stringprintf.cc
index c0f3522..ce20467 100644
--- a/internal/ceres/stringprintf.cc
+++ b/internal/ceres/stringprintf.cc
@@ -28,6 +28,8 @@
 //
 // Author: Sanjay Ghemawat
 
+#include "ceres/stringprintf.h"
+
 #include <cerrno>
 #include <cstdarg>  // For va_list and related operations
 #include <cstdio>   // MSVC requires this for _vsnprintf
diff --git a/internal/ceres/types.cc b/internal/ceres/types.cc
index 1c8a986..2e19322 100644
--- a/internal/ceres/types.cc
+++ b/internal/ceres/types.cc
@@ -39,7 +39,7 @@
 #define CASESTR(x) case x: return #x
 #define STRENUM(x) if (value == #x) { *type = x; return true;}
 
-void UpperCase(string* input) {
+static void UpperCase(string* input) {
   std::transform(input->begin(), input->end(), input->begin(), ::toupper);
 }
 
diff --git a/internal/ceres/visibility.cc b/internal/ceres/visibility.cc
index 9d80654..8e80fd1 100644
--- a/internal/ceres/visibility.cc
+++ b/internal/ceres/visibility.cc
@@ -28,6 +28,8 @@
 //
 // Author: kushalav@google.com (Avanish Kushal)
 
+#include "ceres/visibility.h"
+
 #include <cmath>
 #include <ctime>
 #include <algorithm>