diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index fe60ef5c6..66e492c3d 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -8,7 +8,7 @@ option(SLIC3R_STATIC "Build and link Slic3r statically." ON)
 option(BUILD_EXTRUDE_TIN "Build and link the extrude-tin application." OFF)
 
 # only on newer GCCs: -ftemplate-backtrace-limit=0
-set(CMAKE_CXX_FLAGS "-g ${CMAKE_CXX_FLAGS} -Wall -DM_PI=3.14159265358979323846 -D_GLIBCXX_USE_C99 -DHAS_BOOL -DNOGDI -DBOOST_ASIO_DISABLE_KQUEUE -DNO_PERL")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -DM_PI=3.14159265358979323846 -D_GLIBCXX_USE_C99 -DHAS_BOOL -DNOGDI -DBOOST_ASIO_DISABLE_KQUEUE -DNO_PERL")
 
 if(DEFINED ENV{SLIC3R_VAR_REL})
     set(CMAKE_CXX_FLAGS "-DVAR_REL=$ENV{SLIC3R_VAR_REL}")
@@ -35,7 +35,8 @@ endif()
 
 execute_process(COMMAND git rev-parse --short HEAD OUTPUT_VARIABLE GIT_VERSION ERROR_QUIET)
 
-set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Wall -DSLIC3R_DEBUG")
+set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -g -O0 -Wall -DSLIC3R_DEBUG")
+set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O3 -Wall")
 
 if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 4.7.0)
     if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.7.3)