diff --git a/src/well_known_mime.rs b/src/well_known_mime.rs
index e3c5f0c..c9c292c 100644
--- a/src/well_known_mime.rs
+++ b/src/well_known_mime.rs
@@ -6,7 +6,7 @@ use lazy_static::lazy_static;
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Hash)]
 pub enum Mime {
     /// Well-known mime
-    WellKnown(usize),
+    WellKnown(u16),
     /// Custom mime
     Custom(String),
 }
@@ -35,7 +35,7 @@ impl Display for Mime {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match self {
             Mime::WellKnown(n) => {
-                if let Some(s) = WELL_KNOWN.get(*n) {
+                if let Some(s) = WELL_KNOWN.get(*n as usize) {
                     f.write_str(s)
                 } else {
                     f.write_str("application/octet-stream")
@@ -749,10 +749,10 @@ const WELL_KNOWN : &[&str] = &[
 
 use std::collections::HashMap;
 lazy_static!{
-    static ref MIME_LOOKUP : HashMap<&'static str, usize> = {
+    static ref MIME_LOOKUP : HashMap<&'static str, u16> = {
         let mut map = HashMap::new();
         for (n, entry) in WELL_KNOWN.iter().enumerate() {
-            map.insert(*entry, n);
+            map.insert(*entry, n as u16);
         }
         map
     };