diff --git a/Makefile.am b/Makefile.am
index 2283bb5f..d8d8031c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -132,7 +132,7 @@ libevent_extra_la_LDFLAGS = -release $(RELEASE) -version-info $(VERSION_INFO)
 noinst_HEADERS = util-internal.h mm-internal.h ipv6-internal.h \
 	evrpc-internal.h strlcpy-internal.h evbuffer-internal.h \
 	bufferevent-internal.h http-internal.h event-internal.h \
-	evthread-internal.h ht-internal.h \
+	evthread-internal.h ht-internal.h defer-internal.h \
 	minheap-internal.h log-internal.h evsignal-internal.h evmap-internal.h
 
 include_HEADERS = event.h evhttp.h evdns.h evrpc.h evutil.h event-config.h