diff --git a/MozillaFirefox.changes b/MozillaFirefox.changes
index da01ad6..abbf841 100644
--- a/MozillaFirefox.changes
+++ b/MozillaFirefox.changes
@@ -66,6 +66,7 @@ Sun Nov 15 12:16:53 UTC 2020 - Wolfgang Rosenauer <wr@rosenauer.org>
   NSS >= 3.58
   nodejs >= 10.22.1
 - removed obsolete mozilla-ppc-altivec_static_inline.patch
+- switch to build with clang (as gcc produces only ICEs on TW)
 
 -------------------------------------------------------------------
 Mon Nov  9 10:15:52 UTC 2020 - Wolfgang Rosenauer <wr@rosenauer.org>
diff --git a/MozillaFirefox.spec b/MozillaFirefox.spec
index e543fd7..bdae17f 100644
--- a/MozillaFirefox.spec
+++ b/MozillaFirefox.spec
@@ -41,7 +41,7 @@
 %define do_profiling   0
 
 # upstream default is clang (to use gcc for large parts set to 0)
-%define clang_build 0
+%define clang_build 1
 
 # PIE, full relro
 %define build_hardened 1