diff --git a/factorio/install_mods.sh b/factorio/install_mods.sh
index 39c547b..da77e6e 100755
--- a/factorio/install_mods.sh
+++ b/factorio/install_mods.sh
@@ -8,6 +8,15 @@ for mod in $mods; do
     mod_data=$(curl -s https://mods.factorio.com/api/mods/$mod)
     download_url=$(<<<$mod_data jq -r ".releases[-1].download_url")
     file_name=$(<<<$mod_data jq -r ".releases[-1].file_name")
-    sha1=$(<<<$mod_data jq -r ".releases[-1].sha1") # TODO
-    [ -f $download_dir/$file_name ] || curl --location --no-clobber --output $download_dir/$file_name "https://mods.factorio.com/$download_url?username=$username&token=$token"
+    sha1=$(<<<$mod_data jq -r ".releases[-1].sha1")
+    if [ -f $download_dir/$file_name ]; then
+        current_sha1=$(sha1sum $download_dir/$file_name | awk '{print $1}')
+        if [[ $current_sha1 = $sha1 ]]; then
+            continue
+        else
+        echo $current_sha1 $sha1
+            >&2 echo "Checksum mismatch; re-downloading"
+        fi
+    fi
+    curl --location --output $download_dir/$file_name "https://mods.factorio.com/$download_url?username=$username&token=$token"
 done