diff --git a/irr/src/CMakeLists.txt b/irr/src/CMakeLists.txt
index d5e9d47e716d..5f4d7293c3f3 100644
--- a/irr/src/CMakeLists.txt
+++ b/irr/src/CMakeLists.txt
@@ -14,8 +14,8 @@ endif()
 set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
 
 if(CMAKE_CXX_COMPILER_ID MATCHES "^(GNU|Clang|AppleClang)$")
-	set(CMAKE_CXX_FLAGS_RELEASE "-O3")
-	set(CMAKE_CXX_FLAGS_DEBUG "-g")
+	set(CMAKE_CXX_FLAGS_RELEASE "-O3 $ENV{CPPFLAGS}")
+	set(CMAKE_CXX_FLAGS_DEBUG "-g $ENV{CPPFLAGS}")
 
 	add_compile_options(-Wall -pipe -fno-exceptions)