diff --git a/src/curl.cpp b/src/curl.cpp
index 5737360..1e0a8c7 100644
--- a/src/curl.cpp
+++ b/src/curl.cpp
@@ -2768,8 +2768,8 @@ int S3fsCurl::CompleteMultipartPostRequest(const char* tpath, string& upload_id,
       return -1;
     }
     postContent += "<Part>\n";
-    postContent += "  <PartNumber>" + IntToStr(cnt + 1) + "</PartNumber>\n";
-    postContent += "  <ETag>\""     + parts[cnt]        + "\"</ETag>\n";
+    postContent += "  <PartNumber>" + str(cnt + 1) + "</PartNumber>\n";
+    postContent += "  <ETag>\""     + parts[cnt]   + "\"</ETag>\n";
     postContent += "</Part>\n";
   }  
   postContent += "</CompleteMultipartUpload>\n";
@@ -2983,7 +2983,7 @@ int S3fsCurl::UploadMultipartPostSetup(const char* tpath, int part_num, string&
   }
 
   // make request
-  string request_uri = "partNumber=" + IntToStr(part_num) + "&uploadId=" + upload_id;
+  string request_uri = "partNumber=" + str(part_num) + "&uploadId=" + upload_id;
   string urlargs     = "?" + request_uri;
   string resource;
   string turl;
@@ -3070,7 +3070,7 @@ int S3fsCurl::CopyMultipartPostRequest(const char* from, const char* to, int par
   if(!CreateCurlHandle(true)){
     return -1;
   }
-  string urlargs  = "?partNumber=" + IntToStr(part_num) + "&uploadId=" + upload_id;
+  string urlargs  = "?partNumber=" + str(part_num) + "&uploadId=" + upload_id;
   string resource;
   string turl;
   MakeUrlResource(get_realpath(to).c_str(), resource, turl);
diff --git a/src/string_util.cpp b/src/string_util.cpp
index 6ce5238..1f5d845 100644
--- a/src/string_util.cpp
+++ b/src/string_util.cpp
@@ -85,13 +85,6 @@ string lower(string s)
   return s;
 }
 
-string IntToStr(int n)
-{
-  stringstream result;
-  result << n;
-  return result.str();
-}
-
 string trim_left(const string &s, const string &t /* = SPACES */)
 {
   string d(s);
diff --git a/src/string_util.h b/src/string_util.h
index 003b48f..c61141c 100644
--- a/src/string_util.h
+++ b/src/string_util.h
@@ -45,7 +45,6 @@ std::string trim_left(const std::string &s, const std::string &t = SPACES);
 std::string trim_right(const std::string &s, const std::string &t = SPACES);
 std::string trim(const std::string &s, const std::string &t = SPACES);
 std::string lower(std::string s);
-std::string IntToStr(int);
 std::string get_date_rfc850(void);
 void get_date_sigv3(std::string& date, std::string& date8601);
 std::string get_date_string(time_t tm);
diff --git a/src/test_string_util.cpp b/src/test_string_util.cpp
index 9aab04e..593a083 100644
--- a/src/test_string_util.cpp
+++ b/src/test_string_util.cpp
@@ -18,6 +18,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
+#include <limits>
+#include <stdint.h>
 #include <string>
 
 #include "string_util.h"
@@ -40,5 +42,13 @@ int main(int argc, char *argv[])
   ASSERT_EQUALS(std::string("  1234"), trim_right("  1234"));
   ASSERT_EQUALS(std::string("1234"), trim_right("1234"));
 
+  ASSERT_EQUALS(std::string("0"), str(0));
+  ASSERT_EQUALS(std::string("1"), str(1));
+  ASSERT_EQUALS(std::string("-1"), str(-1));
+  ASSERT_EQUALS(std::string("9223372036854775807"), str(std::numeric_limits<int64_t>::max()));
+  ASSERT_EQUALS(std::string("-9223372036854775808"), str(std::numeric_limits<int64_t>::min()));
+  ASSERT_EQUALS(std::string("0"), str(std::numeric_limits<uint64_t>::min()));
+  ASSERT_EQUALS(std::string("18446744073709551615"), str(std::numeric_limits<uint64_t>::max()));
+
   return 0;
 }