diff --git a/src/testdir/unix.vim b/src/testdir/unix.vim
index 2290ec9..b82c63c 100644
--- a/src/testdir/unix.vim
+++ b/src/testdir/unix.vim
@@ -2,9 +2,12 @@
 " Always use "sh", don't use the value of "$SHELL".
 set shell=sh
 
-" While some tests overwrite $HOME to prevent them from polluting user files,
-" we need to remember the original value so that we can tell external systems
-" where to ask about their own user settings.
-let g:tester_HOME = $HOME
+" Only when the +eval feature is present. 
+if 1
+  " While some tests overwrite $HOME to prevent them from polluting user files,
+  " we need to remember the original value so that we can tell external systems
+  " where to ask about their own user settings.
+  let g:tester_HOME = $HOME
+endif
 
 source setup.vim