diff --git a/adm/cmake/occt_defs_flags.cmake b/adm/cmake/occt_defs_flags.cmake
index 0ed941e496..1b6613515e 100644
--- a/adm/cmake/occt_defs_flags.cmake
+++ b/adm/cmake/occt_defs_flags.cmake
@@ -123,16 +123,6 @@ if ("x${CMAKE_CXX_COMPILER_ID}" STREQUAL "xClang")
   # Optimize size of binaries
   set (CMAKE_SHARED_LINKER_FLAGS "-Wl,-s ${CMAKE_SHARED_LINKER_FLAGS}")
 elseif(MINGW)
-  # Set default release optimization option to O2 instead of O3, since in
-  # some OCCT related examples, this gives significantly smaller binaries
-  # at comparable performace with MinGW-w64.
-  string (REGEX MATCH "-O3" IS_O3_CXX "${CMAKE_CXX_FLAGS_RELEASE}")
-  if (IS_O3_CXX)
-    string (REGEX REPLACE "-O3" "-O2" CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}")
-  else()
-    set (CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
-  endif()
-
   add_definitions(-D_WIN32_WINNT=0x0501)
   # workaround bugs in mingw with vtable export
   set (CMAKE_SHARED_LINKER_FLAGS "-Wl,--export-all-symbols")