diff --git a/libs/sofia-sip/s2check/Makefile.am b/libs/sofia-sip/s2check/Makefile.am
index e2d9914791..ba0bcb41b9 100644
--- a/libs/sofia-sip/s2check/Makefile.am
+++ b/libs/sofia-sip/s2check/Makefile.am
@@ -20,6 +20,7 @@ noinst_LIBRARIES = 	libs2.a
 
 libs2_a_SOURCES = 	s2check.h s2tcase.c \
 			s2_localinfo.h s2_localinfo.c \
+			s2dns.h s2dns.c \
 			s2util.h s2time.c
 
 # ----------------------------------------------------------------------