diff --git a/src/runtime/testdata/testprogcgo/threadpanic_windows.c b/src/runtime/testdata/testprogcgo/threadpanic_windows.c
index 6f896634a6..ba66d0f5c9 100644
--- a/src/runtime/testdata/testprogcgo/threadpanic_windows.c
+++ b/src/runtime/testdata/testprogcgo/threadpanic_windows.c
@@ -8,7 +8,7 @@
 
 void gopanic(void);
 
-static unsigned int
+static unsigned int __attribute__((__stdcall__))
 die(void* x)
 {
 	gopanic();