--- a/bin/ebuild.sh	
+++ a/bin/ebuild.sh	
@@ -35,6 +35,14 @@ unalias -a
 # Unset some variables that break things.
 unset GZIP BZIP BZIP2 CDPATH GREP_OPTIONS GREP_COLOR GLOBIGNORE
 
+# Some USE_EXPAND variables, such as LINGUAS, cause unwanted behavior when
+# empty.  This should be handled via portage.config but it isn't currently
+# designed to do so.
+for x in ${USE_EXPAND}; do
+	[ -z "${!x}" ] && unset ${x}
+done
+unset x
+
 # We need this next line for "die" and "assert". It expands
 # It _must_ preceed all the calls to die and assert.
 shopt -s expand_aliases