diff --git a/install-php-extensions b/install-php-extensions
index 8073322..9f7e401 100755
--- a/install-php-extensions
+++ b/install-php-extensions
@@ -2246,8 +2246,8 @@ installRemoteModule() {
 			fi
 			;;
 		xmldiff)
-			# whether to use system diffmark library
-			addConfigureOption 'with-libdiffmark' 'yes'
+			# whether to use system diffmark library (not yet supported with PHP 8.x)
+			addConfigureOption 'with-libdiffmark' 'no'
 			;;
 		xlswriter)
 			if test -z "$installRemoteModule_version" || test $(compareVersions "$installRemoteModule_version" 1.2.7) -ge 0; then