diff --git a/build.sh b/build.sh
index 6fd90fec8da..153786fed68 100755
--- a/build.sh
+++ b/build.sh
@@ -18,5 +18,9 @@ fi
 
 # Prettify `search_index.json` after `mkdocs`
 # `mkdocs` removed its own prettify few years ago: https://github.com/mkdocs/mkdocs/pull/1128
-python -m json.tool ./site/search/search_index.json >./site/search/search_index_new.json
+if type python3 >/dev/null 2>/dev/null; then
+  python3 -m json.tool ./site/search/search_index.json >./site/search/search_index_new.json
+else
+  python -m json.tool ./site/search/search_index.json >./site/search/search_index_new.json
+fi
 mv -f -- ./site/search/search_index_new.json ./site/search/search_index.json