diff --git a/src/pkg/runtime/darwin/thread.c b/src/pkg/runtime/darwin/thread.c
index c5d8ba4..b35dae0 100644
--- a/src/pkg/runtime/darwin/thread.c
+++ b/src/pkg/runtime/darwin/thread.c
@@ -496,3 +496,9 @@
 	}
 	runtime·panicstring(runtime·sigtab[g->sig].name);
 }
+
+// TODO(rsc): place holder to fix build.
+void
+runtime·osyield(void)
+{
+}