diff --git a/clang/CMakeLists.txt b/clang/CMakeLists.txt
--- a/clang/CMakeLists.txt
+++ b/clang/CMakeLists.txt
@@ -393,8 +393,11 @@
 
 # Add appropriate flags for GCC
 if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-common -Woverloaded-virtual")
-  if (NOT "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-common")
+  if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    # Clang's version of -Woverloaded-virtual is OK, GCC's is too noisy.
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Woverloaded-virtual")
+  else()
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-strict-aliasing")
   endif ()