diff --git a/CMakeLists.txt b/CMakeLists.txt
index f3b6c991d..d540f1187 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -105,9 +105,11 @@ endif()
 set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall")
 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall")
 
-# optimize -O2 even for debug builds
-set (CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -O2")
-set (CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -O2")
+# by detault optimize with -O2 even for debug builds
+set (GCC_OPTIMIZATION_FLAGS "-O2" CACHE STRING "GCC optimization flags")
+message (STATUS "GCC optimization flags: " ${GCC_OPTIMIZATION_FLAGS})
+set (CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} ${GCC_OPTIMIZATION_FLAGS}")
+set (CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} ${GCC_OPTIMIZATION_FLAGS}")
 
 # pkgconfig for required libraries
 find_package(PkgConfig)