diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8e5a703747c2fb5d7ffe3ddbaccf3177d1ff6c31..c0cf546e4ab6d41880be41af4ef5da50dde25a11 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -44,6 +44,10 @@ if( SCALFMM_BUILD_DEBUG )
   ADD_DEFINITIONS(-O0)
 else()
   SET(CMAKE_BUILD_TYPE Release)
+  # force -O2 in release
+  SET(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
+  STRING(REPLACE "-O3" "" CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} )
+  # if compiler is intel add -ip
   IF(CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
     ADD_DEFINITIONS(-ip)
   ENDIF()