diff --git a/.env.sample b/.env.sample
index e292f69fbc8..a2bfa74b844 100644
--- a/.env.sample
+++ b/.env.sample
@@ -3,6 +3,9 @@
 # `postgres://postgres:@localhost/cargo_registry`.
 export DATABASE_URL=""
 
+# If you are running a mirror of crates.io, uncomment this line.
+# export MIRROR=1
+
 # Key to sign and encrypt cookies with. Change this to a long, random string
 # for production.
 export SESSION_KEY="badkey"
diff --git a/src/bin/fill-in-user-id.rs b/src/bin/fill-in-user-id.rs
index df3a17a0588..7a522755866 100644
--- a/src/bin/fill-in-user-id.rs
+++ b/src/bin/fill-in-user-id.rs
@@ -33,6 +33,7 @@ fn main() {
         db_url: env("DATABASE_URL"),
         env: cargo_registry::Env::Production,
         max_upload_size: 0,
+        mirror: false,
     };
     let app = cargo_registry::App::new(&config);
     {
diff --git a/src/bin/server.rs b/src/bin/server.rs
index 3c6ebd2c134..bf0749d65e4 100644
--- a/src/bin/server.rs
+++ b/src/bin/server.rs
@@ -57,6 +57,7 @@ fn main() {
         db_url: env("DATABASE_URL"),
         env: cargo_env,
         max_upload_size: 10 * 1024 * 1024,
+        mirror: env::var("MIRROR").is_ok(),
     };
     let app = cargo_registry::App::new(&config);
     let app = cargo_registry::middleware(Arc::new(app));
diff --git a/src/config.rs b/src/config.rs
index 32833d5653f..76483c58321 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -14,6 +14,7 @@ pub struct Config {
     pub db_url: String,
     pub env: ::Env,
     pub max_upload_size: u64,
+    pub mirror: bool,
 }
 
 impl Config {
diff --git a/src/krate.rs b/src/krate.rs
index fac3625f01f..951ea962479 100644
--- a/src/krate.rs
+++ b/src/krate.rs
@@ -827,6 +827,31 @@ fn read_fill<R: Read + ?Sized>(r: &mut R, mut slice: &mut [u8])
 pub fn download(req: &mut Request) -> CargoResult<Response> {
     let crate_name = &req.params()["crate_id"];
     let version = &req.params()["version"];
+
+    // If we are a mirror, ignore failure to update download counts.
+    // API-only mirrors won't have any crates in their database, and
+    // incrementing the download count will look up the crate in the
+    // database. Mirrors just want to pass along a redirect URL.
+    if req.app().config.mirror {
+        let _ = increment_download_counts(req, crate_name, version);
+    } else {
+        try!(increment_download_counts(req, crate_name, version));
+    }
+
+    let redirect_url = format!("https://{}/crates/{}/{}-{}.crate",
+                               req.app().bucket.host(),
+                               crate_name, crate_name, version);
+
+    if req.wants_json() {
+        #[derive(RustcEncodable)]
+        struct R { url: String }
+        Ok(req.json(&R{ url: redirect_url }))
+    } else {
+        Ok(req.redirect(redirect_url))
+    }
+}
+
+fn increment_download_counts(req: &Request, crate_name: &str, version: &str) -> CargoResult<()> {
     let tx = try!(req.tx());
     let stmt = try!(tx.prepare("SELECT versions.id as version_id
                                 FROM crates
@@ -836,7 +861,7 @@ pub fn download(req: &mut Request) -> CargoResult<Response> {
                                       canon_crate_name($1)
                                   AND versions.num = $2
                                 LIMIT 1"));
-    let rows = try!(stmt.query(&[crate_name, version]));
+    let rows = try!(stmt.query(&[&crate_name, &version]));
     let row = try!(rows.iter().next().chain_error(|| {
         human("crate or version not found")
     }));
@@ -862,19 +887,7 @@ pub fn download(req: &mut Request) -> CargoResult<Response> {
         try!(tx.execute("INSERT INTO version_downloads
                          (version_id) VALUES ($1)", &[&version_id]));
     }
-
-    // Now that we've done our business, redirect to the actual data.
-    let redirect_url = format!("https://{}/crates/{}/{}-{}.crate",
-                               req.app().bucket.host(),
-                               crate_name, crate_name, version);
-
-    if req.wants_json() {
-        #[derive(RustcEncodable)]
-        struct R { url: String }
-        Ok(req.json(&R{ url: redirect_url }))
-    } else {
-        Ok(req.redirect(redirect_url))
-    }
+    Ok(())
 }
 
 /// Handles the `GET /crates/:crate_id/downloads` route.
diff --git a/src/tests/all.rs b/src/tests/all.rs
index e5122359fd2..10fd5609a31 100755
--- a/src/tests/all.rs
+++ b/src/tests/all.rs
@@ -90,6 +90,7 @@ fn app() -> (record::Bomb, Arc<App>, conduit_middleware::MiddlewareBuilder) {
         db_url: env("TEST_DATABASE_URL"),
         env: cargo_registry::Env::Test,
         max_upload_size: 1000,
+        mirror: false,
     };
     INIT.call_once(|| db_setup(&config.db_url));
     let app = App::new(&config);