diff --git a/R-package/src/xgboost_R.cpp b/R-package/src/xgboost_R.cpp
index 35ea0d096..279ef3aea 100644
--- a/R-package/src/xgboost_R.cpp
+++ b/R-package/src/xgboost_R.cpp
@@ -213,7 +213,7 @@ extern "C" {
                                           &olen);
     FILE *fo = utils::FopenCheck(CHAR(asChar(fname)), "w");
     for (size_t i = 0; i < olen; ++i) {
-      fprintf(fo, "booster[%lu]:\n", i);
+      fprintf(fo, "booster[%u]:\n", static_cast<unsigned>(i));
       fprintf(fo, "%s", res[i]);
     }
     fclose(fo);
diff --git a/wrapper/xgboost_wrapper.h b/wrapper/xgboost_wrapper.h
index e03be6265..b0c0052ed 100644
--- a/wrapper/xgboost_wrapper.h
+++ b/wrapper/xgboost_wrapper.h
@@ -7,8 +7,7 @@
  *  can be used to create wrapper of other languages
  */
 #include <cstdio>
-// define uint64_t to be unsigned long
-typedef unsigned long uint64_t;
+#include "../src/utils/utils.h"
 #define XGB_DLL
 
 extern "C" {