diff --git a/docs/source/modeling.rst b/docs/source/modeling.rst
index 8278e8f..33a4098 100644
--- a/docs/source/modeling.rst
+++ b/docs/source/modeling.rst
@@ -53,11 +53,11 @@
       virtual bool Evaluate(double const* const* parameters,
                             double* residuals,
                             double** jacobians) = 0;
-      const vector<int16>& parameter_block_sizes();
+      const vector<int32>& parameter_block_sizes();
       int num_residuals() const;
 
      protected:
-      vector<int16>* mutable_parameter_block_sizes();
+      vector<int32>* mutable_parameter_block_sizes();
       void set_num_residuals(int num_residuals);
     };
 
diff --git a/include/ceres/cost_function.h b/include/ceres/cost_function.h
index 8013e96..722ac77 100644
--- a/include/ceres/cost_function.h
+++ b/include/ceres/cost_function.h
@@ -115,7 +115,7 @@
                         double* residuals,
                         double** jacobians) const = 0;
 
-  const vector<int16>& parameter_block_sizes() const {
+  const vector<int32>& parameter_block_sizes() const {
     return parameter_block_sizes_;
   }
 
@@ -124,7 +124,7 @@
   }
 
  protected:
-  vector<int16>* mutable_parameter_block_sizes() {
+  vector<int32>* mutable_parameter_block_sizes() {
     return &parameter_block_sizes_;
   }
 
@@ -135,7 +135,7 @@
  private:
   // Cost function signature metadata: number of inputs & their sizes,
   // number of outputs (residuals).
-  vector<int16> parameter_block_sizes_;
+  vector<int32> parameter_block_sizes_;
   int num_residuals_;
   CERES_DISALLOW_COPY_AND_ASSIGN(CostFunction);
 };
diff --git a/include/ceres/cost_function_to_functor.h b/include/ceres/cost_function_to_functor.h
index fa1012d..0d01f77 100644
--- a/include/ceres/cost_function_to_functor.h
+++ b/include/ceres/cost_function_to_functor.h
@@ -127,7 +127,7 @@
         << N3 << ", " << N4 << ", " << N5 << ", " << N6 << ", " << N7 << ", "
         << N8 << ", " << N9;
 
-    const vector<int16>& parameter_block_sizes =
+    const vector<int32>& parameter_block_sizes =
         cost_function->parameter_block_sizes();
     const int num_parameter_blocks =
         (N0 > 0) + (N1 > 0) + (N2 > 0) + (N3 > 0) + (N4 > 0) +
@@ -679,7 +679,7 @@
   template <typename JetT>
   bool EvaluateWithJets(const JetT** inputs, JetT* output) const {
     const int kNumParameters =  N0 + N1 + N2 + N3 + N4 + N5 + N6 + N7 + N8 + N9;
-    const vector<int16>& parameter_block_sizes =
+    const vector<int32>& parameter_block_sizes =
         cost_function_->parameter_block_sizes();
     const int num_parameter_blocks = parameter_block_sizes.size();
     const int num_residuals = cost_function_->num_residuals();
@@ -732,7 +732,7 @@
       output[i].v.setZero();
 
       for (int j = 0; j < num_parameter_blocks; ++j) {
-        const int16 block_size = parameter_block_sizes[j];
+        const int32 block_size = parameter_block_sizes[j];
         for (int k = 0; k < parameter_block_sizes[j]; ++k) {
           output[i].v +=
               jacobian_blocks[j][i * block_size + k] * inputs[j][k].v;
diff --git a/include/ceres/dynamic_numeric_diff_cost_function.h b/include/ceres/dynamic_numeric_diff_cost_function.h
index c2bfb32..2b6e826 100644
--- a/include/ceres/dynamic_numeric_diff_cost_function.h
+++ b/include/ceres/dynamic_numeric_diff_cost_function.h
@@ -104,7 +104,7 @@
         << "You must call DynamicNumericDiffCostFunction::SetNumResiduals() "
         << "before DynamicNumericDiffCostFunction::Evaluate().";
 
-    const vector<int16>& block_sizes = parameter_block_sizes();
+    const vector<int32>& block_sizes = parameter_block_sizes();
     CHECK(!block_sizes.empty())
         << "You must call DynamicNumericDiffCostFunction::AddParameterBlock() "
         << "before DynamicNumericDiffCostFunction::Evaluate().";
diff --git a/include/ceres/gradient_checker.h b/include/ceres/gradient_checker.h
index 3ec8056..79ebae5 100644
--- a/include/ceres/gradient_checker.h
+++ b/include/ceres/gradient_checker.h
@@ -119,7 +119,7 @@
     // Do a consistency check between the term and the template parameters.
     CHECK_EQ(M, term->num_residuals());
     const int num_residuals = M;
-    const vector<int16>& block_sizes = term->parameter_block_sizes();
+    const vector<int32>& block_sizes = term->parameter_block_sizes();
     const int num_blocks = block_sizes.size();
 
     CHECK_LE(num_blocks, 5) << "Unable to test functions that take more "
diff --git a/internal/ceres/block_structure.h b/internal/ceres/block_structure.h
index f509067..2abb36a 100644
--- a/internal/ceres/block_structure.h
+++ b/internal/ceres/block_structure.h
@@ -47,7 +47,7 @@
 
 class BlockStructureProto;
 
-typedef int16 BlockSize;
+typedef int32 BlockSize;
 
 struct Block {
   Block() : size(-1), position(-1) {}
diff --git a/internal/ceres/cost_function_to_functor_test.cc b/internal/ceres/cost_function_to_functor_test.cc
index 90ccc82..fd828ce 100644
--- a/internal/ceres/cost_function_to_functor_test.cc
+++ b/internal/ceres/cost_function_to_functor_test.cc
@@ -42,9 +42,9 @@
   EXPECT_EQ(cost_function.num_residuals(),
             actual_cost_function.num_residuals());
   const int num_residuals = cost_function.num_residuals();
-  const vector<int16>& parameter_block_sizes =
+  const vector<int32>& parameter_block_sizes =
       cost_function.parameter_block_sizes();
-  const vector<int16>& actual_parameter_block_sizes =
+  const vector<int32>& actual_parameter_block_sizes =
       actual_cost_function.parameter_block_sizes();
   EXPECT_EQ(parameter_block_sizes.size(),
             actual_parameter_block_sizes.size());
diff --git a/internal/ceres/covariance_test.cc b/internal/ceres/covariance_test.cc
index 4680244..471b223 100644
--- a/internal/ceres/covariance_test.cc
+++ b/internal/ceres/covariance_test.cc
@@ -125,7 +125,7 @@
 class UnaryCostFunction: public CostFunction {
  public:
   UnaryCostFunction(const int num_residuals,
-                    const int16 parameter_block_size,
+                    const int32 parameter_block_size,
                     const double* jacobian)
       : jacobian_(jacobian, jacobian + num_residuals * parameter_block_size) {
     set_num_residuals(num_residuals);
@@ -158,8 +158,8 @@
 class BinaryCostFunction: public CostFunction {
  public:
   BinaryCostFunction(const int num_residuals,
-                     const int16 parameter_block1_size,
-                     const int16 parameter_block2_size,
+                     const int32 parameter_block1_size,
+                     const int32 parameter_block2_size,
                      const double* jacobian1,
                      const double* jacobian2)
       : jacobian1_(jacobian1,
diff --git a/internal/ceres/gradient_checking_cost_function.cc b/internal/ceres/gradient_checking_cost_function.cc
index 5503013..bca22e6 100644
--- a/internal/ceres/gradient_checking_cost_function.cc
+++ b/internal/ceres/gradient_checking_cost_function.cc
@@ -93,7 +93,7 @@
             DO_NOT_TAKE_OWNERSHIP,
             relative_step_size);
 
-    const vector<int16>& parameter_block_sizes =
+    const vector<int32>& parameter_block_sizes =
         function->parameter_block_sizes();
     for (int i = 0; i < parameter_block_sizes.size(); ++i) {
       finite_diff_cost_function->AddParameterBlock(parameter_block_sizes[i]);
@@ -117,7 +117,7 @@
     int num_residuals = function_->num_residuals();
 
     // Make space for the jacobians of the two methods.
-    const vector<int16>& block_sizes = function_->parameter_block_sizes();
+    const vector<int32>& block_sizes = function_->parameter_block_sizes();
     vector<Matrix> term_jacobians(block_sizes.size());
     vector<Matrix> finite_difference_jacobians(block_sizes.size());
     vector<double*> term_jacobian_pointers(block_sizes.size());
diff --git a/internal/ceres/gradient_checking_cost_function_test.cc b/internal/ceres/gradient_checking_cost_function_test.cc
index ac06503..caba2f6 100644
--- a/internal/ceres/gradient_checking_cost_function_test.cc
+++ b/internal/ceres/gradient_checking_cost_function_test.cc
@@ -264,7 +264,7 @@
 // Trivial cost function that accepts a single argument.
 class UnaryCostFunction : public CostFunction {
  public:
-  UnaryCostFunction(int num_residuals, int16 parameter_block_size) {
+  UnaryCostFunction(int num_residuals, int32 parameter_block_size) {
     set_num_residuals(num_residuals);
     mutable_parameter_block_sizes()->push_back(parameter_block_size);
   }
@@ -284,8 +284,8 @@
 class BinaryCostFunction: public CostFunction {
  public:
   BinaryCostFunction(int num_residuals,
-                     int16 parameter_block1_size,
-                     int16 parameter_block2_size) {
+                     int32 parameter_block1_size,
+                     int32 parameter_block2_size) {
     set_num_residuals(num_residuals);
     mutable_parameter_block_sizes()->push_back(parameter_block1_size);
     mutable_parameter_block_sizes()->push_back(parameter_block2_size);
@@ -305,9 +305,9 @@
 class TernaryCostFunction: public CostFunction {
  public:
   TernaryCostFunction(int num_residuals,
-                      int16 parameter_block1_size,
-                      int16 parameter_block2_size,
-                      int16 parameter_block3_size) {
+                      int32 parameter_block1_size,
+                      int32 parameter_block2_size,
+                      int32 parameter_block3_size) {
     set_num_residuals(num_residuals);
     mutable_parameter_block_sizes()->push_back(parameter_block1_size);
     mutable_parameter_block_sizes()->push_back(parameter_block2_size);
diff --git a/internal/ceres/problem_impl.cc b/internal/ceres/problem_impl.cc
index 09eed9e..37cd351 100644
--- a/internal/ceres/problem_impl.cc
+++ b/internal/ceres/problem_impl.cc
@@ -224,7 +224,7 @@
            cost_function->parameter_block_sizes().size());
 
   // Check the sizes match.
-  const vector<int16>& parameter_block_sizes =
+  const vector<int32>& parameter_block_sizes =
       cost_function->parameter_block_sizes();
 
   if (!options_.disable_all_safety_checks) {
diff --git a/internal/ceres/problem_test.cc b/internal/ceres/problem_test.cc
index 3d0ea82..858600d 100644
--- a/internal/ceres/problem_test.cc
+++ b/internal/ceres/problem_test.cc
@@ -56,7 +56,7 @@
 // Trivial cost function that accepts a single argument.
 class UnaryCostFunction : public CostFunction {
  public:
-  UnaryCostFunction(int num_residuals, int16 parameter_block_size) {
+  UnaryCostFunction(int num_residuals, int32 parameter_block_size) {
     set_num_residuals(num_residuals);
     mutable_parameter_block_sizes()->push_back(parameter_block_size);
   }
@@ -76,8 +76,8 @@
 class BinaryCostFunction: public CostFunction {
  public:
   BinaryCostFunction(int num_residuals,
-                     int16 parameter_block1_size,
-                     int16 parameter_block2_size) {
+                     int32 parameter_block1_size,
+                     int32 parameter_block2_size) {
     set_num_residuals(num_residuals);
     mutable_parameter_block_sizes()->push_back(parameter_block1_size);
     mutable_parameter_block_sizes()->push_back(parameter_block2_size);
@@ -97,9 +97,9 @@
 class TernaryCostFunction: public CostFunction {
  public:
   TernaryCostFunction(int num_residuals,
-                      int16 parameter_block1_size,
-                      int16 parameter_block2_size,
-                      int16 parameter_block3_size) {
+                      int32 parameter_block1_size,
+                      int32 parameter_block2_size,
+                      int32 parameter_block3_size) {
     set_num_residuals(num_residuals);
     mutable_parameter_block_sizes()->push_back(parameter_block1_size);
     mutable_parameter_block_sizes()->push_back(parameter_block2_size);
diff --git a/internal/ceres/residual_block_test.cc b/internal/ceres/residual_block_test.cc
index 1e03e7d..b37f50f 100644
--- a/internal/ceres/residual_block_test.cc
+++ b/internal/ceres/residual_block_test.cc
@@ -43,9 +43,9 @@
 class TernaryCostFunction: public CostFunction {
  public:
   TernaryCostFunction(int num_residuals,
-                      int16 parameter_block1_size,
-                      int16 parameter_block2_size,
-                      int16 parameter_block3_size) {
+                      int32 parameter_block1_size,
+                      int32 parameter_block2_size,
+                      int32 parameter_block3_size) {
     set_num_residuals(num_residuals);
     mutable_parameter_block_sizes()->push_back(parameter_block1_size);
     mutable_parameter_block_sizes()->push_back(parameter_block2_size);