diff --git a/src/libraries/liboop/Makefile.am b/src/libraries/liboop/Makefile.am
index b04b31be1cc90062c910130a267471541db0e31e..dbc99a176fc2852704bb613db509c08440a15284 100644
--- a/src/libraries/liboop/Makefile.am
+++ b/src/libraries/liboop/Makefile.am
@@ -7,6 +7,9 @@
 # See the file COPYING for details.
 
 AUTOMAKE_OPTIONS = foreign 1.2
+
+AM_CPPFLAGS = -I$(srcdir)/../adns/src
+
 noinst_LIBRARIES = liboop.a
 INCLUDES = $(GLIB_INCLUDES) $(TCL_INCLUDES) $(WWW_INCLUDES)