diff --git a/cmake/QtCompilerOptimization.cmake b/cmake/QtCompilerOptimization.cmake
index e1d363afab2..d2932d0ca10 100644
--- a/cmake/QtCompilerOptimization.cmake
+++ b/cmake/QtCompilerOptimization.cmake
@@ -92,7 +92,12 @@ endif()
 
 # Windows MSVC
 if(MSVC)
-    set(QT_CFLAGS_OPTIMIZE "-O2 -Ob3") # -Ob3 was introduced in Visual Studio 2019 version 16.0
+    set(QT_CFLAGS_OPTIMIZE "-O2")
+    if(NOT CLANG)
+        # -Ob3 was introduced in Visual Studio 2019 version 16.0
+        # However clang-cl can't recognize it.
+        string(APPEND QT_CFLAGS_OPTIMIZE " -Ob3 ")
+    endif()
     set(QT_CFLAGS_OPTIMIZE_DEBUG "-Od")
     set(QT_CFLAGS_OPTIMIZE_SIZE "-O1")
     set(QT_CFLAGS_OPTIMIZE_VALID_VALUES "/O2" "/O1" "/Od" "/Ob0" "/Ob1" "/Ob2" "/Ob3" "/O0" "-O0")