diff --git a/usr.bin/xlint/lint1/param.h b/usr.bin/xlint/lint1/param.h
index 94d8947a3b52..7d31373ccf02 100644
--- a/usr.bin/xlint/lint1/param.h
+++ b/usr.bin/xlint/lint1/param.h
@@ -95,6 +95,9 @@
 #elif __mips__
 #define PTRDIFF_IS_LONG		0
 #define SIZEOF_IS_ULONG		0
+#elif __aarch64__
+#define PTRDIFF_IS_LONG		1
+#define SIZEOF_IS_ULONG		1
 #else
 #error unknown machine type
 #endif