diff --git a/CMakeLists.txt b/CMakeLists.txt
index e6d66b8d..f54dd7ba 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -34,21 +34,24 @@ set(CMAKE_C_STANDARD_REQUIRED true)
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_C_STANDARD 11)
 include(GenerateExportHeader)
-set(CMAKE_CXX_FLAGS " -Wall -pedantic -Werror -Wno-deprecated-declarations -D_GLIBCXX_USE_CXX11_ABI=0 -fstack-protector-strong --param=ssp-buffer-size=4 -O3 -D_FORTIFY_SOURCE=2 ${CMAKE_CXX_FLAGS}")
+set(CMAKE_CXX_FLAGS "-Wall -pedantic -Werror -Wno-deprecated-declarations -D_GLIBCXX_USE_CXX11_ABI=0 -fstack-protector-strong --param=ssp-buffer-size=4 ${CMAKE_CXX_FLAGS}")
 if(UNIX AND APPLE)
-    set(CMAKE_CXX_FLAGS " -stdlib=libc++ ${CMAKE_CXX_FLAGS}")
+    set(CMAKE_CXX_FLAGS "-stdlib=libc++ ${CMAKE_CXX_FLAGS}")
 endif()
-# FIXME: GCC 12 complains about some random stuff in QuaZip. Need to fix this later
+# FIXME: GCC 12 complains about some random stuff in bundled QuaZip. Need to fix this later
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     set(CMAKE_CXX_FLAGS "-Wno-error=stringop-overflow ${CMAKE_CXX_FLAGS}")
 endif()
-set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Werror=return-type")
 
 # Fix build with Qt 5.13
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DQT_NO_DEPRECATED_WARNINGS=Y")
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DQT_DISABLE_DEPRECATED_BEFORE=0x050C00")
 
+# set CXXFLAGS for build targets
+set(CMAKE_CXX_FLAGS_DEBUG "-O1 ${CMAKE_CXX_FLAGS}")
+set(CMAKE_CXX_FLAGS_RELEASE "-O2 -D_FORTIFY_SOURCE=2 ${CMAKE_CXX_FLAGS}")
+
 option(ENABLE_LTO "Enable Link Time Optimization" off)
 
 if(ENABLE_LTO)