diff --git a/src/common/hist_util.cc b/src/common/hist_util.cc
index 5dc9049c4..890d18b86 100644
--- a/src/common/hist_util.cc
+++ b/src/common/hist_util.cc
@@ -663,7 +663,11 @@ void GHistIndexBlockMatrix::Init(const GHistIndexMatrix& gmat,
  * \brief fill a histogram by zeroes
  */
 void InitilizeHistByZeroes(GHistRow hist, size_t begin, size_t end) {
+#if defined(XGBOOST_STRICT_R_MODE) && XGBOOST_STRICT_R_MODE == 1
+  std::fill(hist.begin() + begin, hist.begin() + end, tree::GradStats());
+#else  // defined(XGBOOST_STRICT_R_MODE) && XGBOOST_STRICT_R_MODE == 1
   memset(hist.data() + begin, '\0', (end-begin)*sizeof(tree::GradStats));
+#endif  // defined(XGBOOST_STRICT_R_MODE) && XGBOOST_STRICT_R_MODE == 1
 }
 
 /*!
diff --git a/src/common/observer.h b/src/common/observer.h
index f150fa880..2048fc5cd 100644
--- a/src/common/observer.h
+++ b/src/common/observer.h
@@ -15,15 +15,15 @@
 #include "xgboost/base.h"
 #include "xgboost/tree_model.h"
 
-#if defined(XGBOOST_STRICT_R_MODE)
+#if defined(XGBOOST_STRICT_R_MODE) && XGBOOST_STRICT_R_MODE == 1
 #define OBSERVER_PRINT LOG(INFO)
 #define OBSERVER_ENDL ""
 #define OBSERVER_NEWLINE ""
-#else
+#else  // defined(XGBOOST_STRICT_R_MODE) && XGBOOST_STRICT_R_MODE == 1
 #define OBSERVER_PRINT std::cout
 #define OBSERVER_ENDL std::endl
 #define OBSERVER_NEWLINE "\n"
-#endif  // defined(XGBOOST_STRICT_R_MODE)
+#endif  // defined(XGBOOST_STRICT_R_MODE) && XGBOOST_STRICT_R_MODE == 1
 
 namespace xgboost {
 /*\brief  An observer for logging internal data structures.