diff --git a/build_tools/build_lexicon_filter.sh b/build_tools/build_lexicon_filter.sh
index 2b49b3718..167a390ce 100755
--- a/build_tools/build_lexicon_filter.sh
+++ b/build_tools/build_lexicon_filter.sh
@@ -18,7 +18,7 @@ rm -f lexicon.tmp lexicon_catalog.tmp lexicon_catalog.txt lexicon.txt
 FUNCTIONS_DIR_FILES=${1}/*.fish
 COMPLETIONS_DIR_FILES=${2}/*.fish
 
-SED=${3:-$(which sed)}
+SED=${3:-$(command -v sed)}
 
 # Scan sources for commands/functions/binaries/colours. If GNU sed was portable, this could be much smarter.
 $SED <command_list_toc.txt >>lexicon.tmp -n \