diff --git a/misc/cgo/test/sigprocmask_linux.c b/misc/cgo/test/sigprocmask_linux.c
index 6597e985ac..518c533fa4 100644
--- a/misc/cgo/test/sigprocmask_linux.c
+++ b/misc/cgo/test/sigprocmask_linux.c
@@ -22,6 +22,7 @@ static void* sigthreadfunc(void* unused) {
 	sigaddset(&mask, SIGIO);
 	sigprocmask(SIG_BLOCK, &mask, NULL);
 	IntoGoAndBack();
+	return NULL;
 }
 
 int RunSigThread() {