diff --git a/appveyor/test_task.bat b/appveyor/test_task.bat
index c55bd7ea054..65b3ea0e9de 100644
--- a/appveyor/test_task.bat
+++ b/appveyor/test_task.bat
@@ -78,6 +78,8 @@ rem set SSLEAY_CONF=
 
 rem prepare for OPcache
 if "%OPCACHE%" equ "1" set OPCACHE_OPTS=-d opcache.enable=1 -d opcache.enable_cli=1 -d opcache.protect_memory=1 -d opcache.jit_buffer_size=16M
+rem work-around for failing to dl(mysqli) with OPcache (https://github.com/php/php-src/issues/8508)
+if "%OPCACHE%" equ "1" set OPCACHE_OPTS=%OPCACHE_OPTS% -d extension=mysqli
 
 rem prepare for enchant
 mkdir C:\usr\local\lib\enchant-2