diff --git a/libgo/go/runtime/testdata/testprogcgo/callback.go b/libgo/go/runtime/testdata/testprogcgo/callback.go
index 7d9d68d..7b58f4a 100644
--- a/libgo/go/runtime/testdata/testprogcgo/callback.go
+++ b/libgo/go/runtime/testdata/testprogcgo/callback.go
@@ -7,6 +7,9 @@
 package main
 
 /*
+#cgo CFLAGS: -pthread
+#cgo LDFLAGS: -pthread
+
 #include <pthread.h>
 
 void go_callback();