diff --git a/contrib/arrow-cmake/CMakeLists.txt b/contrib/arrow-cmake/CMakeLists.txt
index efd139d45ae..3ba24f49498 100644
--- a/contrib/arrow-cmake/CMakeLists.txt
+++ b/contrib/arrow-cmake/CMakeLists.txt
@@ -70,6 +70,10 @@ add_custom_command(OUTPUT orc_proto.pb.h orc_proto.pb.cc
         --cpp_out="${CMAKE_CURRENT_BINARY_DIR}"
         "${PROTO_DIR}/orc_proto.proto")
 
+# arrow-cmake cmake file calling orc cmake subroutine which detects certain compiler features. 
+# Apple Clang compiler failed to compile this code without specifying c++11 standard. 
+# As result these compiler features detected as absent. In result it failed to compile orc itself.
+# In orc makefile there is code that sets flags, but arrow-cmake ignores these flags.
 if (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
   set (CXX11_FLAGS "-std=c++0x")
 endif()