diff --git a/crypto/rand/rand_win.c b/crypto/rand/rand_win.c
index a28fb6ea5..692a13eac 100644
--- a/crypto/rand/rand_win.c
+++ b/crypto/rand/rand_win.c
@@ -168,7 +168,7 @@ typedef DWORD (WINAPI *GETQUEUESTATUS)(UINT);
 
 typedef HANDLE (WINAPI *CREATETOOLHELP32SNAPSHOT)(DWORD, DWORD);
 typedef BOOL (WINAPI *CLOSETOOLHELP32SNAPSHOT)(HANDLE);
-typedef BOOL (WINAPI *HEAP32FIRST)(LPHEAPENTRY32, DWORD, ULONG_PTR);
+typedef BOOL (WINAPI *HEAP32FIRST)(LPHEAPENTRY32, DWORD, SIZE_T);
 typedef BOOL (WINAPI *HEAP32NEXT)(LPHEAPENTRY32);
 typedef BOOL (WINAPI *HEAP32LIST)(HANDLE, LPHEAPLIST32);
 typedef BOOL (WINAPI *PROCESS32)(HANDLE, LPPROCESSENTRY32);