diff --git a/win/build-deps.cmd b/win/build-deps.cmd
index 854f901ecf..754dd7a89f 100644
--- a/win/build-deps.cmd
+++ b/win/build-deps.cmd
@@ -805,7 +805,6 @@ IF DEFINED QT6_HOST_INSTALL_DIR (
 IF "%QT6_TARGET_INSTALLED%"=="TRUE" IF "%QT6_HOST_INSTALLED%"=="TRUE" (
     echo Found existing "%QT6_INSTALL_DIR%" for %BUILD_CFG%, skipping
     IF DEFINED QT6_HOST_INSTALL_DIR echo Found existing Qt host tools at "%QT6_HOST_INSTALL_DIR%", skipping
-    call :MarkInstallation
     goto %NEXT_DEPENDENCY_LABEL%
 )
 
@@ -819,6 +818,9 @@ IF NOT "%QT6_TARGET_INSTALLED%"=="TRUE" (
     REM Keep the install lean by filtering archives: qtbase provides
     REM Core/Gui/Widgets (and the Qt6::CorePrivate target), qtsvg provides
     REM Qt6::Svg. Both are base-Qt archives, not add-on modules.
+    REM Qt's official archives always bundle both RelWithDebInfo and Debug builds together.
+    REM aqtinstall has no option to download only one of them, or other configs
+    REM (Release/MinSizeRel) instead.
     %AQT_PYTHON% -m aqt install-qt windows desktop %QT6_VERSION% %QT6_ARCH% -O "%QT6_AQT_OUTPUT_DIR%" --archives qtbase qtsvg
     IF ERRORLEVEL 1 GOTO :Error
 )
@@ -862,7 +864,6 @@ IF DEFINED QT6_HOST_INSTALL_DIR (
     )
 )
 
-call :MarkInstallation
 goto %NEXT_DEPENDENCY_LABEL%
 
 :manifold
diff --git a/win/installers.py b/win/installers.py
index 6c69d18439..752a97c72b 100644
--- a/win/installers.py
+++ b/win/installers.py
@@ -845,7 +845,6 @@ def install_qt6(
         logger.info(f"Found existing '{QT6_INSTALL_DIR}' for {build_cfg}, skipping")
         if QT6_CROSS_COMPILING:
             logger.info(f"Found existing Qt host tools at '{QT6_HOST_INSTALL_DIR}', skipping")
-        mark_installation(QT6_INSTALL_DIR, build_cfg)
         return
 
     def install_via_pip(python_exe: str) -> tuple[str, ...]:
@@ -869,6 +868,9 @@ def install_qt6(
         AQT_CMD = install_via_pip(AQT_PYTHON)
 
     def aqt_install_qt(arch: str, output_dir: Path) -> None:
+        # Qt's official archives always bundle both RelWithDebInfo and Debug builds together.
+        # aqtinstall has no option to download only one of them, or other configs
+        # (Release/MinSizeRel) instead.
         run_streamed(
             *AQT_CMD,
             "install-qt",
@@ -912,9 +914,6 @@ def install_qt6(
         for path in QT6_HOST_EXPECTED_FILES:
             require_exists("Qt6 host installation", path)
 
-    # TODO: check if it's actually needed, since we don't use check it.
-    mark_installation(QT6_INSTALL_DIR, build_cfg)
-
 
 def install_python(
     vs_cfg_vars: VsCfgResult,