diff --git a/CMakeLists.txt b/CMakeLists.txt
index 74aaf422..d859bbe0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -73,8 +73,8 @@ if (ENABLE_LTO)
     set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
 endif()
 
-set(CMAKE_C_FLAGS_DEBUG "-Og")
-set(CMAKE_CXX_FLAGS_DEBUG "-Og")
+set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -Og")
+set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Og")
 set(CMAKE_C_FLAGS_RELEASE "-O3")
 set(CMAKE_CXX_FLAGS_RELEASE "-O3")