diff --git a/cmake/QtInternalTargets.cmake b/cmake/QtInternalTargets.cmake
index 6a9ba2ab4e..1485726f0f 100644
--- a/cmake/QtInternalTargets.cmake
+++ b/cmake/QtInternalTargets.cmake
@@ -6,6 +6,12 @@ function(qt_internal_set_warnings_are_errors_flags target)
         if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "3.0.0")
             list(APPEND flags -Werror -Wno-error=\#warnings -Wno-error=deprecated-declarations)
         endif()
+        if(CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows")
+            # Clang will otherwise show error about inline method conflicting with dllimport class attribute in tools
+            # (this was tested with Clang 10)
+            #    error: 'QString::operator[]' redeclared inline; 'dllimport' attribute ignored [-Werror,-Wignored-attributes]
+            list(APPEND flags -Wno-ignored-attributes)
+        endif()
     elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "AppleClang")
         # using AppleClang
         # Apple clang 4.0+