diff --git a/adm/cmake/occt_defs_flags.cmake b/adm/cmake/occt_defs_flags.cmake
index 6271a35043..974f9784dd 100644
--- a/adm/cmake/occt_defs_flags.cmake
+++ b/adm/cmake/occt_defs_flags.cmake
@@ -147,14 +147,14 @@ elseif (CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX OR (CMAKE_CXX_COMPIL
     # /GL (whole program optimization) is similar to -flto (Link Time Optimization) in GCC/Clang.
     # /GF (eliminate duplicate strings) doesn't have a direct equivalent in GCC/Clang, but the compilers do string pooling automatically.
     # /Gy (enable function-level linking) is similar to -ffunction-sections in GCC/Clang.
-    set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O3 -fomit-frame-pointer -flto -ffunction-sections")
-    set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O3 -fomit-frame-pointer -flto -ffunction-sections")
+    set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2 -fomit-frame-pointer -flto -ffunction-sections")
+    set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O2 -fomit-frame-pointer -flto -ffunction-sections")
 
     # Link-Time Code Generation(LTCG) is requared for Whole Program Optimisation(GL)
     set(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} -flto")
-    set(CMAKE_SHARED_LINKER_FLAGS_RELEASE "${CMAKE_SHARED_LINKER_FLAGS_RELEASE} -flto")
-    set(CMAKE_STATIC_LINKER_FLAGS_RELEASE "${CMAKE_STATIC_LINKER_FLAGS_RELEASE} -flto")
-    set(CMAKE_MODULE_LINKER_FLAGS_RELEASE "${CMAKE_MODULE_LINKER_FLAGS_RELEASE} -flto")
+    set(CMAKE_SHARED_LINKER_FLAGS_RELEASE "${CMAKE_SHARED_LINKER_FLAGS_RELEASE} -flto -Wl,--gc-sections")
+    set(CMAKE_STATIC_LINKER_FLAGS_RELEASE "${CMAKE_STATIC_LINKER_FLAGS_RELEASE} -flto -Wl,--gc-sections")
+    set(CMAKE_MODULE_LINKER_FLAGS_RELEASE "${CMAKE_MODULE_LINKER_FLAGS_RELEASE} -flto -Wl,--gc-sections")
   endif()
   if (CMAKE_CXX_COMPILER_ID MATCHES "[Cc][Ll][Aa][Nn][Gg]")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wshorten-64-to-32")