diff --git a/gtk/a11y/Makefile.am b/gtk/a11y/Makefile.am
index b6b3b44b9a..d9b2a2315b 100644
--- a/gtk/a11y/Makefile.am
+++ b/gtk/a11y/Makefile.am
@@ -128,6 +128,7 @@ libgail_la_CPPFLAGS = \
 	-I$(top_srcdir)/gtk		\
 	-I$(top_builddir)/gtk		\
 	-DGTK_VERSION=\"$(GTK_VERSION)\"\
+	-DGTK_COMPILATION		\
 	-DGDK_DISABLE_DEPRECATED	\
 	-DGTK_DISABLE_DEPRECATED	\
 	$(AM_CPPFLAGS)