diff --git a/R-package/src/xgboost_R.cc b/R-package/src/xgboost_R.cc
index 82ba36828..dcf1228ce 100644
--- a/R-package/src/xgboost_R.cc
+++ b/R-package/src/xgboost_R.cc
@@ -229,27 +229,6 @@ SEXP XGBoosterCreate_R(SEXP dmats) {
   return ret;
 }
 
-SEXP XGBoosterGetAttr_R(SEXP handle, SEXP name) {
-  const char* ret;
-  R_API_BEGIN();
-  int success;
-  CHECK_CALL(XGBoosterGetAttr(R_ExternalPtrAddr(handle),
-                             CHAR(asChar(name)),
-                             &ret,
-                             &success));
-  R_API_END();
-  return mkString(ret);
-}
-
-SEXP XGBoosterSetAttr_R(SEXP handle, SEXP name, SEXP val) {
-  R_API_BEGIN();
-  CHECK_CALL(XGBoosterSetAttr(R_ExternalPtrAddr(handle),
-                              CHAR(asChar(name)),
-                              CHAR(asChar(val))));
-  R_API_END();
-  return R_NilValue;
-}
-
 SEXP XGBoosterSetParam_R(SEXP handle, SEXP name, SEXP val) {
   R_API_BEGIN();
   CHECK_CALL(XGBoosterSetParam(R_ExternalPtrAddr(handle),
@@ -388,3 +367,32 @@ SEXP XGBoosterDumpModel_R(SEXP handle, SEXP fmap, SEXP with_stats) {
   R_API_END();
   return out;
 }
+
+SEXP XGBoosterGetAttr_R(SEXP handle, SEXP name) {
+  SEXP out;
+  R_API_BEGIN();
+  int success;
+  const char *val;
+  CHECK_CALL(XGBoosterGetAttr(R_ExternalPtrAddr(handle),
+                              CHAR(asChar(name)),
+                              &val,
+                              &success));
+  if (success) {
+    out = PROTECT(allocVector(STRSXP, 1));
+    SET_STRING_ELT(out, 0, mkChar(val));
+  } else {
+    out = PROTECT(R_NilValue);
+  }
+  UNPROTECT(1);
+  R_API_END();
+  return out;
+}
+
+SEXP XGBoosterSetAttr_R(SEXP handle, SEXP name, SEXP val) {
+  R_API_BEGIN();
+  CHECK_CALL(XGBoosterSetAttr(R_ExternalPtrAddr(handle),
+                              CHAR(asChar(name)),
+                              CHAR(asChar(val))));
+  R_API_END();
+  return R_NilValue;
+}
diff --git a/R-package/src/xgboost_R.h b/R-package/src/xgboost_R.h
index 1d8e2d567..daf304529 100644
--- a/R-package/src/xgboost_R.h
+++ b/R-package/src/xgboost_R.h
@@ -101,23 +101,6 @@ XGB_DLL SEXP XGDMatrixNumCol_R(SEXP handle);
  */
 XGB_DLL SEXP XGBoosterCreate_R(SEXP dmats);
 
-/*!
- * \brief get learner attribute value
- * \param handle handle
- * \param name  attribute name
- * \return string containing attribute value
- */
-XGB_DLL SEXP XGBoosterGetAttr_R(SEXP handle, SEXP name);
-
-/*!
- * \brief set learner attribute value
- * \param handle handle
- * \param name  attribute name
- * \param val attribute value
- * \return R_NilValue
- */
-XGB_DLL SEXP XGBoosterSetAttr_R(SEXP handle, SEXP name, SEXP val);
-
 /*!
  * \brief set parameters
  * \param handle handle
@@ -202,4 +185,22 @@ XGB_DLL SEXP XGBoosterModelToRaw_R(SEXP handle);
  * \param with_stats whether dump statistics of splits
  */
 XGB_DLL SEXP XGBoosterDumpModel_R(SEXP handle, SEXP fmap, SEXP with_stats);
+
+/*!
+ * \brief get learner attribute value
+ * \param handle handle
+ * \param name  attribute name
+ * \return character containing attribute value
+ */
+XGB_DLL SEXP XGBoosterGetAttr_R(SEXP handle, SEXP name);
+
+/*!
+ * \brief set learner attribute value
+ * \param handle handle
+ * \param name  attribute name
+ * \param val attribute value
+ * \return R_NilValue
+ */
+XGB_DLL SEXP XGBoosterSetAttr_R(SEXP handle, SEXP name, SEXP val);
+
 #endif  // XGBOOST_WRAPPER_R_H_ // NOLINT(*)