Index: CMakeLists.txt
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -165,7 +165,6 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
         set(NORMAL_CXX_FLAGS "${NORMAL_CXX_FLAGS} -Wsuggest-override")
     endif()
 
-    set(RELEASE_CXX_FLAGS "-O2")
     set(DEBUG_CXX_FLAGS "-g -O0")
     set(TEST_CXX_FLAGS "-pthread")
     add_definitions(-DNOEXCEPT=noexcept -DHAVE_DEMANGLE)
@@ -182,7 +181,6 @@ elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
 
     set(NORMAL_CXX_FLAGS "-Wall -Wold-style-cast -pedantic-errors -Wmissing-prototypes")
     set(NORMAL_CXX_FLAGS "${NORMAL_CXX_FLAGS} -Wno-error=deprecated-declarations") # updated version of physfs is not available on some platforms so we keep using deprecated functions, see #958
-    set(RELEASE_CXX_FLAGS "-O2")
     set(DEBUG_CXX_FLAGS "-g -O0")
     set(TEST_CXX_FLAGS "-pthread")
     add_definitions(-DNOEXCEPT=noexcept -DHAVE_DEMANGLE)
