diff --git a/configure.ac b/configure.ac
index b1ce80c6f06..6ebb9667004 100644
--- a/configure.ac
+++ b/configure.ac
@@ -468,7 +468,7 @@ AC_ARG_WITH([ns],[AS_HELP_STRING([--with-ns],
 [use Nextstep (macOS Cocoa or GNUstep) windowing system.
 On by default on macOS.])],[],[with_ns=maybe])
 OPTION_DEFAULT_OFF([w32], [use native MS Windows GUI in a Cygwin build])
-OPTION_DEFAULT_OFF([pgtk], [use pure GTK build without reliance on X libs (Wayland support) - Experimental])
+OPTION_DEFAULT_OFF([pgtk], [use pure GTK build without reliance on X libs (Wayland support) (requires cairo) - Experimental])
 
 OPTION_DEFAULT_ON([gpm],[don't use -lgpm for mouse support on a GNU/Linux console])
 OPTION_DEFAULT_ON([dbus],[don't compile with D-Bus support])