diff --git a/posix-amd64/getcallerpc.c b/posix-amd64/getcallerpc.c
index 553c750..3614c59 100644
--- a/posix-amd64/getcallerpc.c
+++ b/posix-amd64/getcallerpc.c
@@ -1,8 +1,8 @@
 #include "u.h"
 #include "libc.h"
 
-ulong
+uintptr
 getcallerpc(void *a)
 {
-	return ((ulong*)a)[-1];
+	return ((uintptr*)a)[-1];
 }