diff --git a/Makefile.am b/Makefile.am
index 74ff592dce..b7dbdcd9d7 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -524,6 +524,7 @@ libnm_core_tests_cppflags = \
 	-I$(srcdir)/libnm-core \
 	-I$(builddir)/libnm-core \
 	-I$(srcdir)/libnm-core/tests \
+	-I$(builddir)/libnm-core/tests \
 	-DNETWORKMANAGER_COMPILATION \
 	$(GLIB_CFLAGS) \
 	-DTEST_CERT_DIR=\"$(abs_srcdir)/libnm-core/tests/certs\"