diff --git a/doc/reference/cogl/Makefile.am b/doc/reference/cogl/Makefile.am
index 74d96eacf..9d3645e70 100644
--- a/doc/reference/cogl/Makefile.am
+++ b/doc/reference/cogl/Makefile.am
@@ -115,7 +115,7 @@ expand_content_files = \
 # e.g. INCLUDES=-I$(top_srcdir) -I$(top_builddir) $(GTK_DEBUG_FLAGS)
 # e.g. GTKDOC_LIBS=$(top_builddir)/gtk/$(gtktargetlib)
 
-INCLUDES=-I$(top_srcdir) -I$(top_srcdir)/clutter -I$(top_srcdir)/clutter/cogl -I$(top_builddir)/clutter/cogl $(CLUTTER_CFLAGS)
+INCLUDES=-I$(top_srcdir) -I$(top_srcdir)/clutter -I$(top_srcdir)/clutter/cogl -I$(top_builddir)/clutter/cogl -DCOGL_ENABLE_EXPERIMENTAL_API $(CLUTTER_CFLAGS)
 GTKDOC_LIBS=$(top_builddir)/clutter/libclutter-@CLUTTER_WINSYS@-@CLUTTER_API_VERSION@.la $(CLUTTER_LIBS)
 
 # This includes the standard gtk-doc make rules, copied by gtkdocize.