diff --git a/pkgs/development/compilers/ccl/default.nix b/pkgs/development/compilers/ccl/default.nix
index 761ae5ba0197..cd8433444963 100644
--- a/pkgs/development/compilers/ccl/default.nix
+++ b/pkgs/development/compilers/ccl/default.nix
@@ -121,6 +121,8 @@ stdenv.mkDerivation rec {
     homepage    = "https://ccl.clozure.com/";
     maintainers = with maintainers; [ raskin muflax tohl ];
     platforms   = attrNames options;
+    # assembler failures during build, x86_64-darwin broken since 2020-10-14
+    broken      = (stdenv.isDarwin && stdenv.isx86_64);
     license     = licenses.asl20;
   };
 }