diff --git a/include/mapnik/proj_transform.hpp b/include/mapnik/proj_transform.hpp
index 5fec3c589..daf84b52c 100644
--- a/include/mapnik/proj_transform.hpp
+++ b/include/mapnik/proj_transform.hpp
@@ -44,16 +44,16 @@ public:
     bool is_known() const;
     bool forward (double& x, double& y , double& z) const;
     bool backward (double& x, double& y , double& z) const;
-    bool forward (double *x, double *y , double *z, int point_count, int offset = 1) const;
-    bool backward (double *x, double *y , double *z, int point_count, int offset = 1) const;
+    bool forward (double *x, double *y , double *z, std::size_t point_count, std::size_t offset = 1) const;
+    bool backward (double *x, double *y , double *z, std::size_t point_count, std::size_t offset = 1) const;
     bool forward (geometry::point<double> & p) const;
     bool backward (geometry::point<double> & p) const;
     unsigned int forward (std::vector<geometry::point<double>> & ls) const;
     unsigned int backward (std::vector<geometry::point<double>> & ls) const;
     bool forward (box2d<double> & box) const;
     bool backward (box2d<double> & box) const;
-    bool forward (box2d<double> & box, int points) const;
-    bool backward (box2d<double> & box, int points) const;
+    bool forward (box2d<double> & box, std::size_t points) const;
+    bool backward (box2d<double> & box, std::size_t points) const;
 private:
     PJ_CONTEXT* ctx_ = nullptr;
     PJ* transform_ = nullptr;
diff --git a/src/proj_transform.cpp b/src/proj_transform.cpp
index 529780eb7..380b55b3a 100644
--- a/src/proj_transform.cpp
+++ b/src/proj_transform.cpp
@@ -214,7 +214,7 @@ unsigned int proj_transform::forward (std::vector<geometry::point<double>> & ls)
     return 0;
 }
 
-bool proj_transform::forward (double * x, double * y , double * z, int point_count, int offset) const
+bool proj_transform::forward (double * x, double * y , double * z, std::size_t point_count, std::size_t offset) const
 {
     if (is_source_equal_dest_)
         return true;
@@ -240,7 +240,7 @@ bool proj_transform::forward (double * x, double * y , double * z, int point_cou
     return true;
 }
 
-bool proj_transform::backward (double * x, double * y , double * z, int point_count, int offset) const
+bool proj_transform::backward (double * x, double * y , double * z, std::size_t point_count, std::size_t offset) const
 {
     if (is_source_equal_dest_)
         return true;
@@ -372,7 +372,7 @@ bool proj_transform::backward (box2d<double> & box) const
 // Alternative is to provide proper clipping box
 // in the target srs by setting map 'maximum-extent'
 
-bool proj_transform::backward(box2d<double>& env, int points) const
+bool proj_transform::backward(box2d<double>& env, std::size_t points) const
 {
     if (is_source_equal_dest_)
         return true;
@@ -411,7 +411,7 @@ bool proj_transform::backward(box2d<double>& env, int points) const
     return true;
 }
 
-bool proj_transform::forward(box2d<double>& env, int points) const
+bool proj_transform::forward(box2d<double>& env, std::size_t points) const
 {
     if (is_source_equal_dest_)
         return true;