diff --git a/src/main.rs b/src/main.rs
index 21ac233..099ec2a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -108,6 +108,10 @@ async fn main() -> ResBE<()> {
         }
     };
     
+    if numparal <= 0 {
+        eprintln!("Invalid value for numdl: {}", numparal);
+        exit(1);
+    }
 
     let boost = match arguments.value_of("boost") {
         Some(it) => it,
@@ -121,12 +125,24 @@ async fn main() -> ResBE<()> {
             exit(1);
         }
     };
+    
+    if boost <= 0 {
+        eprintln!("Invalid value for boost: {}", boost);
+        exit(1);
+    }
 
     let is_zippy = arguments.is_present("zippyshare");
 
     if arguments.is_present("listfile") {
 
-        let listfile = arguments.value_of("listfile").unwrap();
+        let s_listfile = arguments.value_of("listfile").unwrap();
+
+        let listfile = Path::new(s_listfile);
+
+        if !listfile.is_file() {
+            eprintln!("Listfile '{}' does not exist!", s_listfile);
+            exit(1);
+        }
 
         let ifile = std::fs::File::open(listfile)?;
 
@@ -177,7 +193,10 @@ async fn download_multiple(urls: Vec<String>, outdir: &str, numparal: i32, boost
     let outdir = Path::new(outdir);
 
     if !outdir.exists() {
-        std::fs::create_dir_all(outdir)?;
+        if let Err(_e) = std::fs::create_dir_all(outdir) {
+            eprintln!("Error creating output directory '{}'", outdir.to_str().unwrap());
+            exit(1);
+        }
     }
 
     let t_start = SystemTime::now();