diff --git a/sys/src/lib/c/port/_assert.c b/sys/src/lib/c/port/_assert.c
index 34d15c2..0f456de 100644
--- a/sys/src/lib/c/port/_assert.c
+++ b/sys/src/lib/c/port/_assert.c
@@ -19,4 +19,5 @@ _assert(const char *s)
 		(*__assert)((char*)s);
 	fprint(2, "assert failed: %s\n", s);
 	abort();
+	__builtin_unreachable();
 }