diff --git a/src/lib/dns/tests/Makefile.am b/src/lib/dns/tests/Makefile.am
index ea7d4dd9b5..560db50818 100644
--- a/src/lib/dns/tests/Makefile.am
+++ b/src/lib/dns/tests/Makefile.am
@@ -1,4 +1,4 @@
-AM_CPPFLAGS = -I$(top_builddir)/src/lib -I$(top_builddir)/src/lib
+AM_CPPFLAGS = -I$(top_builddir)/src/lib
 
 CLEANFILES = *.gcno *.gcda