diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1359da1fe..5664ec5e5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -26,8 +26,8 @@ add_definitions(${LLVM_DEFINITIONS})
 set(CMAKE_C_STANDARD 11)
 set(CMAKE_CXX_STANDARD 17)
 
-set(CMAKE_CXX_FLAGS_RELEASE "-O3")
-set(CMAKE_C_FLAGS_RELEASE "-O3")
+set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O3")
+set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O3")
 
 set(LLVM_LINK_COMPONENTS
         AllTargetsAsmParsers