diff --git a/Formula/scantailor.rb b/Formula/scantailor.rb
index a1201a4228..b6272bbc33 100644
--- a/Formula/scantailor.rb
+++ b/Formula/scantailor.rb
@@ -19,7 +19,7 @@ class Scantailor < Formula
   depends_on :x11
 
   fails_with :clang do
-    build 318
+    build 421
     cause "calling a private constructor of class 'mcalc::Mat<double>'"
   end