diff --git a/llvm/test/tools/llvm-ar/mri-utf8.test b/llvm/test/tools/llvm-ar/mri-utf8.test
--- a/llvm/test/tools/llvm-ar/mri-utf8.test
+++ b/llvm/test/tools/llvm-ar/mri-utf8.test
@@ -16,8 +16,11 @@
 # include arguments with non-ascii characters.
 # Python on Linux defaults to ASCII encoding unless the
 # environment specifies otherwise, so it is explicitly set.
+# The locale chosen is C.UTF-8 as being the most likely to
+# be available on a system, in particular on a minimal
+# system like a docker image.
 # The reliance the test has on this locale is not ideal,
 # however alternate solutions have been difficult due to 
 # behaviour differences with python 2 vs python 3,
-# and linux vs windows.
-RUN: env LANG=en_US.UTF-8 %python -c "assert open(u'\U000000A3.txt', 'rb').read() == b'contents\n'"
+# and linux vs windows. The C.UTF-8 locale is chosen
+RUN: env LANG=C.UTF-8 %python -c "assert open(u'\xA3.txt', 'rb').read() == b'contents\n'"