diff -up thunderbird-68.1.1/build/autoconf/icu.m4.icu thunderbird-68.1.1/build/autoconf/icu.m4
--- thunderbird-68.1.1/build/autoconf/icu.m4.icu	2019-10-04 09:48:47.337041046 +0200
+++ thunderbird-68.1.1/build/autoconf/icu.m4	2019-10-04 09:52:32.046670353 +0200
@@ -78,7 +78,7 @@ if test -n "$USE_ICU"; then
     # TODO: the l is actually endian-dependent
     # We could make this set as 'l' or 'b' for little or big, respectively,
     # but we'd need to check in a big-endian version of the file.
-    ICU_DATA_FILE="icudt${version}l.dat"
+    ICU_DATA_FILE="icudt${version}b.dat"
 fi
 
 AC_SUBST(MOZ_ICU_VERSION)