diff --git a/src/book/book.rs b/src/book/book.rs
index 7998b704..af23e785 100644
--- a/src/book/book.rs
+++ b/src/book/book.rs
@@ -404,7 +404,10 @@ fn load_chapter<P: AsRef<Path>>(
         if !location.exists() && !link_location.is_absolute() {
             src_dir = src_dir_fallback;
             location = src_dir.join(link_location);
-            debug!("Falling back to {}", location.display());
+            debug!(
+                "Falling back to default translation in path \"{}\"",
+                location.display()
+            );
         }
         if !location.exists() && cfg.build.create_missing {
             create_missing(&location, &link)
@@ -586,7 +589,10 @@ more text.
     fn cant_load_a_nonexistent_chapter() {
         let link = Link::new("Chapter 1", "/foo/bar/baz.md");
 
-        let got = load_chapter(&link, "", "", Vec::new(), &Config::default());
+        let mut cfg = Config::default();
+        cfg.build.create_missing = false;
+
+        let got = load_chapter(&link, "", "", Vec::new(), &cfg);
         assert!(got.is_err());
     }
 
diff --git a/src/cmd/serve.rs b/src/cmd/serve.rs
index f1a09f74..d18d3388 100644
--- a/src/cmd/serve.rs
+++ b/src/cmd/serve.rs
@@ -188,7 +188,8 @@ async fn serve(
         // Redirect root to the default translation directory, if serving a localized book.
         // NOTE: This can't be `/{lang_ident}`, or the static assets won't get loaded.
         // BUG: Redirects get cached if you change the --language parameter,
-        // meaning you'll get a 404 unless you disable cache in the developer tools.
+        // meaning you'll get a 404 unless you disable the cache in Developer
+        // Tools.
         let index_for_language = format!("/{}/index.html", lang_ident)
             .parse::<Uri>()
             .unwrap();
@@ -211,6 +212,7 @@ async fn serve(
         // The fallback route for 404 errors
         let fallback_route = warp::fs::file(build_dir.join(file_404))
             .map(|reply| warp::reply::with_status(reply, warp::http::StatusCode::NOT_FOUND));
+
         let routes = livereload.or(book_route).or(fallback_route);
         warp::serve(routes).run(address).await;
     };
diff --git a/src/config.rs b/src/config.rs
index 68875c1d..fa49677c 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -297,9 +297,9 @@ impl Config {
         }
     }
 
-    /// Get the fallback source directory of a book. For example, if chapters
-    /// are missing in a localization, the links will gracefully degrade to the
-    /// files that exist in this directory.
+    /// Get the fallback source directory of a book. If chapters/sections are
+    /// missing in a localization, any links to them will gracefully degrade to
+    /// the files that exist in this directory.
     pub fn get_fallback_src_path(&self) -> PathBuf {
         match self.language.default_language() {
             // Languages have been specified, assume directory structure with
@@ -417,7 +417,7 @@ impl<'de> Deserialize<'de> for Config {
 
             if default_languages != 1  {
                 return Err(D::Error::custom(
-                    "If languages are specified, exactly one must be set as 'default'",
+                    "If [languages] table is specified, exactly one entry must be set as 'default'",
                 ));
             }
         }
@@ -784,7 +784,7 @@ pub struct LanguageConfig(pub HashMap<String, Language>);
 pub struct Language {
     /// Human-readable name of the language.
     pub name: String,
-    /// If true, this language is the default. There can only be one default
+    /// If true, this language is the default. There must be exactly one default
     /// language in the config.
     pub default: bool,
 }
diff --git a/tests/testing.rs b/tests/testing.rs
index 2b2c0fd0..51e23d82 100644
--- a/tests/testing.rs
+++ b/tests/testing.rs
@@ -7,7 +7,7 @@ use mdbook::MDBook;
 #[test]
 fn mdbook_can_correctly_test_a_passing_book() {
     let temp = DummyBook::new().with_passing_test(true).build().unwrap();
-    let mut md = MDBook::load(temp.path()).unwrap();
+    let md = MDBook::load(temp.path()).unwrap();
 
     let result = md.test(vec![]);
     assert!(
@@ -20,7 +20,7 @@ fn mdbook_can_correctly_test_a_passing_book() {
 #[test]
 fn mdbook_detects_book_with_failing_tests() {
     let temp = DummyBook::new().with_passing_test(false).build().unwrap();
-    let mut md = MDBook::load(temp.path()).unwrap();
+    let md = MDBook::load(temp.path()).unwrap();
 
     assert!(md.test(vec![]).is_err());
 }