diff --git a/nu/moonbit.nu b/nu/moonbit.nu
index 77f8d74..7a6671c 100644
--- a/nu/moonbit.nu
+++ b/nu/moonbit.nu
@@ -24,7 +24,7 @@ export-env {
 
 # Download binary file from CLI_HOST with aira2c or `http get`
 def fetch-bin [ bin: string, download_path: string ] {
-  if (is-installed aria2c) {
+  if not (is-installed aria2c) {
     aria2c --allow-overwrite $'($CLI_HOST)/($download_path)/($bin)'
   } else {
     http get $'($CLI_HOST)/($download_path)/($bin)' | save --progress --force $bin