diff --git a/src/user/drv.uart/main.cpp b/src/user/drv.uart/main.cpp
index bb20b26..ae383c7 100644
--- a/src/user/drv.uart/main.cpp
+++ b/src/user/drv.uart/main.cpp
@@ -81,7 +81,7 @@ channel_pump_loop()
 }
 
 void
-pump_proc()
+pump_proc(void *)
 {
     j6_process_exit(channel_pump_loop());
 }
diff --git a/src/user/testapp/main.cpp b/src/user/testapp/main.cpp
index 2fd9d22..64d2d23 100644
--- a/src/user/testapp/main.cpp
+++ b/src/user/testapp/main.cpp
@@ -21,7 +21,7 @@ constexpr uintptr_t stack_top = 0xf80000000;
 uint32_t flipflop = 0;
 
 void
-thread_proc()
+thread_proc(void*)
 {
     j6_log("sub thread starting");