diff --git a/appveyor/install_kiwix-lib.cmd b/appveyor/install_kiwix-lib.cmd
index 42461f1..c0a8b10 100644
--- a/appveyor/install_kiwix-lib.cmd
+++ b/appveyor/install_kiwix-lib.cmd
@@ -2,6 +2,7 @@ REM ========================================================
 REM Install kiwix-lib
 git clone https://github.com/kiwix/kiwix-lib.git || exit /b 1
 cd kiwix-lib
+set CPPFLAGS="-I%EXTRA_DIR%/include"
 meson . build --prefix %EXTRA_DIR% --default-library static --buildtype release || exit /b 1
 cd build
 ninja || exit /b 1