diff --git a/CMakeLists.txt b/CMakeLists.txt
index 420a8ecd..c3f6b49b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -225,7 +225,7 @@ else()
     if(OPTIMISE)
         if (NOT CMAKE_BUILD_TYPE MATCHES MINSIZEREL)
             set(OPT_C_FLAG "-O3")
-            set(OPT_CXX_FLAG "-O2")
+            set(OPT_CXX_FLAG "-O3")
         else ()
             set(OPT_C_FLAG "-Os")
             set(OPT_CXX_FLAG "-Os")