diff --git a/src/testdir/test_compiler.vim b/src/testdir/test_compiler.vim
index 781bac6..4b710df 100644
--- a/src/testdir/test_compiler.vim
+++ b/src/testdir/test_compiler.vim
@@ -7,10 +7,8 @@
   CheckExecutable perl
   CheckFeature quickfix
 
-  " $LANG changes the output of Perl.
-  if $LANG != ''
-    unlet $LANG
-  endif
+  let save_LC_ALL = $LC_ALL
+  let $LC_ALL= "C"
 
   " %:S does not work properly with 'shellslash' set
   let save_shellslash = &shellslash
@@ -40,6 +38,7 @@
   let &shellslash = save_shellslash
   call delete('Xfoo.pl')
   bw!
+  let $LC_ALL = save_LC_ALL
 endfunc
 
 func GetCompilerNames()