diff --git a/adm/cmake/occt_defs_flags.cmake b/adm/cmake/occt_defs_flags.cmake
index 484002d1aa..0ed941e496 100644
--- a/adm/cmake/occt_defs_flags.cmake
+++ b/adm/cmake/occt_defs_flags.cmake
@@ -111,7 +111,18 @@ elseif (CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX OR "${CMAKE_CXX_COMP
   endif()
 endif()
 
-if(MINGW)
+if ("x${CMAKE_CXX_COMPILER_ID}" STREQUAL "xClang")
+  if (APPLE)
+    # CLang can be used with both libstdc++ and libc++, however on OS X libstdc++ is outdated.
+    set (CMAKE_CXX_FLAGS "-std=c++0x -stdlib=libc++ ${CMAKE_CXX_FLAGS}")
+  elseif(NOT WIN32)
+    # CLang for Windows (at least CLang 8.0 distributed with VS 2019)
+    # does not support option "-std=c++0x"
+    set (CMAKE_CXX_FLAGS "-std=c++0x ${CMAKE_CXX_FLAGS}")
+  endif()
+  # Optimize size of binaries
+  set (CMAKE_SHARED_LINKER_FLAGS "-Wl,-s ${CMAKE_SHARED_LINKER_FLAGS}")
+elseif(MINGW)
   # Set default release optimization option to O2 instead of O3, since in
   # some OCCT related examples, this gives significantly smaller binaries
   # at comparable performace with MinGW-w64.
@@ -122,25 +133,19 @@ if(MINGW)
     set (CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O2")
   endif()
 
-  set (CMAKE_CXX_FLAGS "-std=gnu++0x ${CMAKE_CXX_FLAGS}")
   add_definitions(-D_WIN32_WINNT=0x0501)
   # workaround bugs in mingw with vtable export
   set (CMAKE_SHARED_LINKER_FLAGS "-Wl,--export-all-symbols")
-elseif ("x${CMAKE_CXX_COMPILER_ID}" STREQUAL "xClang")
-  if (APPLE)
-    # CLang can be used with both libstdc++ and libc++, however on OS X libstdc++ is outdated.
-    set (CMAKE_CXX_FLAGS "-std=c++0x -stdlib=libc++ ${CMAKE_CXX_FLAGS}")
-  elseif(NOT WIN32)
-    # CLang for Windows (at least CLang 8.0 distributed with VS 2019) 
-    # does not support option "-std=c++0x"
-    set (CMAKE_CXX_FLAGS "-std=c++0x ${CMAKE_CXX_FLAGS}")
-  endif()
-elseif (DEFINED CMAKE_COMPILER_IS_GNUCXX)
-  set (CMAKE_CXX_FLAGS "-std=c++0x ${CMAKE_CXX_FLAGS}")
-endif()
 
-# Optimize size of binaries
-if (CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX OR MINGW)
+  # Require C++11
+  set (CMAKE_CXX_FLAGS "-std=gnu++0x ${CMAKE_CXX_FLAGS}")
+  # Optimize size of binaries
+  set (CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -s")
+  set (CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -s")
+elseif (DEFINED CMAKE_COMPILER_IS_GNUCXX)
+  # Require C++11
+  set (CMAKE_CXX_FLAGS "-std=c++0x ${CMAKE_CXX_FLAGS}")
+  # Optimize size of binaries
   set (CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -s")
   set (CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -s")
 endif()