diff --git a/plugins/input/csv/csv_datasource.cpp b/plugins/input/csv/csv_datasource.cpp
index 4d26bdd0f..f76656311 100644
--- a/plugins/input/csv/csv_datasource.cpp
+++ b/plugins/input/csv/csv_datasource.cpp
@@ -127,7 +127,7 @@ void csv_datasource::parse_csv(T& stream,
                                std::string const& quote) const
 {
     stream.seekg (0, std::ios::end);
-    int file_length_ = stream.tellg();
+    file_length_ = stream.tellg();
     
     if (filesize_max_ > 0)
     {
@@ -151,7 +151,7 @@ void csv_datasource::parse_csv(T& stream,
     char newline = '\n';
     int newline_count = 0;
     int carriage_count = 0;
-    for(std::size_t idx = 0; idx < file_length_; idx++)
+    for(unsigned idx = 0; idx < file_length_; idx++)
     {
         char c = static_cast<char>(stream.get());
         if (c == '\n')
@@ -357,7 +357,7 @@ void csv_datasource::parse_csv(T& stream,
 
     int feature_count(1);
     bool extent_initialized = false;
-    int num_headers = headers_.size();
+    unsigned num_headers = headers_.size();
     mapnik::transcoder tr(desc_.get_encoding());
 
     while (std::getline(stream,csv_line,newline))
@@ -387,7 +387,7 @@ void csv_datasource::parse_csv(T& stream,
             // early return for strict mode
             if (strict_)
             {
-                int num_fields = std::distance(beg,tok.end());
+                unsigned num_fields = std::distance(beg,tok.end());
                 if (num_fields != num_headers)
                 {
                     std::ostringstream s;
@@ -405,7 +405,7 @@ void csv_datasource::parse_csv(T& stream,
             bool null_geom = false;
             std::vector<std::string> collected;
             
-            for (int i = 0; i < num_headers; ++i)
+            for (unsigned i = 0; i < num_headers; ++i)
             {
                 std::string fld_name(headers_.at(i));
                 collected.push_back(fld_name);
diff --git a/plugins/input/csv/csv_datasource.hpp b/plugins/input/csv/csv_datasource.hpp
index e3fbb1683..d2e51bf8c 100644
--- a/plugins/input/csv/csv_datasource.hpp
+++ b/plugins/input/csv/csv_datasource.hpp
@@ -29,7 +29,7 @@ class csv_datasource : public mapnik::datasource
       mutable mapnik::box2d<double> extent_;
       mutable std::string filename_;
       mutable std::string inline_string_;
-      mutable int file_length_;
+      mutable unsigned file_length_;
       mutable int row_limit_;
       mutable std::vector<mapnik::feature_ptr> features_;
       mutable std::string escape_;