Export TLS support in gl.pc.
diff --git a/configure.ac b/configure.ac
index c00ecd0..9cbced5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -808,13 +808,19 @@
 fi
 
 dnl
-dnl More DRI setup
+dnl TLS detection
 dnl
+
 AC_ARG_ENABLE([glx-tls],
     [AS_HELP_STRING([--enable-glx-tls],
         [enable TLS support in GLX @<:@default=disabled@:>@])],
     [GLX_USE_TLS="$enableval"],
     [GLX_USE_TLS=no])
+AC_SUBST(GLX_TLS, ${GLX_USE_TLS})
+
+dnl
+dnl More DRI setup
+dnl
 dnl Directory for DRI drivers
 AC_ARG_WITH([dri-driverdir],
     [AS_HELP_STRING([--with-dri-driverdir=DIR],