diff --git a/sample/Makefile.am b/sample/Makefile.am
index 937e94ef..6a148148 100644
--- a/sample/Makefile.am
+++ b/sample/Makefile.am
@@ -5,16 +5,16 @@ AM_CPPFLAGS = -I$(top_srcdir) -I$(top_srcdir)/compat -I$(top_srcdir)/include -I.
 
 noinst_PROGRAMS = event-test time-test signal-test dns-example hello-world http-server
 
-event_test_sources = event-test.c
-time_test_sources = time-test.c
-signal_test_sources = signal-test.c
-dns_example_sources = dns-example.c
-hello_world_sources = hello-world.c
-http_server_sources = http-server.c
+event_test_SOURCES = event-test.c
+time_test_SOURCES = time-test.c
+signal_test_SOURCES = signal-test.c
+dns_example_SOURCES = dns-example.c
+hello_world_SOURCES = hello-world.c
+http_server_SOURCES = http-server.c
 
 if OPENSSL
 noinst_PROGRAMS += le-proxy
-le_proxy_sources = le-proxy.c
+le_proxy_SOURCES = le-proxy.c
 le_proxy_LDADD = $(LDADD) ../libevent_openssl.la -lssl -lcrypto
 endif