diff --git a/install/unix/source.xml b/install/unix/source.xml
index 5ff56c5ee3e8..274533eb53d4 100644
--- a/install/unix/source.xml
+++ b/install/unix/source.xml
@@ -9,7 +9,7 @@
     <link xlink:href="&url.gnu.make;">GNU <command>make</command></link>
    </member>
    <member>
-    A C compiler (as of PHP 8.0.0, C99 compatibility is assumed)
+    A C compiler (as of PHP 8.0.0, C99 compatibility is required; as of PHP 8.4.0, C11 compatibility is required)
    </member>
    <member>
     A web server