diff --git a/CMakeLists.txt b/CMakeLists.txt
index 89bd81e..2c2877c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,9 +7,12 @@ SET(IZUMO_ERRDIR      "${CMAKE_INSTALL_PREFIX}/share/izumo/log")
 SET(IR_UNIX_DIR       "/tmp/.iroha_unix")
 SET(IR_UNIX_SOCKNAME  "IROHA")
 
-if (NOT CMAKE_BUILD_TYPE)
-  set(CMAKE_BUILD_TYPE Debug)
+#select the release build type by default to get optimization flags
+if(NOT CMAKE_BUILD_TYPE)
+  set(CMAKE_BUILD_TYPE "Release")
+  message(STATUS "Build type not specified: defaulting to release.")
 endif(NOT CMAKE_BUILD_TYPE)
+set(CMAKE_BUILD_TYPE ${CMAKE_BUILD_TYPE} CACHE STRING "")
 
 INCLUDE_DIRECTORIES(${PROJECT_SOURCE_DIR}/include)
 INCLUDE_DIRECTORIES(${PROJECT_SOURCE_DIR}/include/RK)