diff --git a/cmake/QtCompilerOptimization.cmake b/cmake/QtCompilerOptimization.cmake
index ac542e94510..6485b5792e1 100644
--- a/cmake/QtCompilerOptimization.cmake
+++ b/cmake/QtCompilerOptimization.cmake
@@ -101,7 +101,7 @@ if(MSVC)
     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 ")
+        string(APPEND QT_CFLAGS_OPTIMIZE " -Ob3")
     endif()
     set(QT_CFLAGS_OPTIMIZE_DEBUG "-Od")
     set(QT_CFLAGS_OPTIMIZE_SIZE "-O1")