diff --git a/src/pkg/runtime/linux/os.h b/src/pkg/runtime/linux/os.h
index c36813a9bf..fd6ccffc39 100644
--- a/src/pkg/runtime/linux/os.h
+++ b/src/pkg/runtime/linux/os.h
@@ -7,4 +7,4 @@ int32	futex(uint32*, int32, uint32, Timespec*, uint32*, uint32);
 int32	clone(int32, void*, M*, G*, void(*)(void));
 
 struct Sigaction;
-void	rt_sigaction(int64, struct Sigaction*, void*, uint64);
+void	rt_sigaction(uintptr, struct Sigaction*, void*, uintptr);